","[{\n \"@id\": \"http://dbpedia.org/resource/John_Lennon\",\n \"http://xmlns.com/foaf/0.1/name\": [{\"@value\": \"John Lennon\"}],\n \"http://schema.org/birthDate\": [\n {\"@value\": \"1940-10-09\", \"@type\": \"http://www.w3.org/2001/XMLSchema#date\"}\n ],\n \"http://schema.org/spouse\": [\n {\"@id\": \"http://dbpedia.org/resource/Cynthia_Lennon\"}\n ]\n}]","http://dbpedia.org/resource/John_Lennon","John Lennon","schema:birthDate","1940-10-09","xsd:date","schema:spouse","http://dbpedia.org/resource/Cynthia_Lennon","@prefix foaf: .\n@prefix schema: .\n@prefix xsd: .\n\n foaf:name \"John Lennon\";\n schema:birthDate \"1940-10-09\"^^xsd:date;\n schema:spouse .","Defining how such data may be used is beyond the scope of this specification.\n The embedded JSON-LD document might be extracted as is or, e.g., be\n interpreted as RDF.","If JSON-LD content is extracted as RDF [","], it "," be expanded into an\n ","RDF Dataset","Deserialize JSON-LD to RDF Algorithm","\n [","]. Unless a specific script is targeted\n (see ","§ 7.3 Locating a Specific JSON-LD Script Element","),\n all ","script elements","\n with "," be processed and merged\n into a single "," with equivalent "," contained in\n separate script elements treated as if they were in a single document (i.e.,\n blank nodes are shared between different JSON-LD script elements).","\n Example 145: Combining multiple JSON-LD script elements into a single dataset\n ","HTML Embedded (Input)","
Data describing Dave
\n\n\n
Data describing Gregg
\n","https://digitalbazaar.com/author/dlongley/","@prefix schema: .\n\n a schema:Person;\n schema:name \"Dave Longley\" .\n\n a schema:Person;\n schema:name \"Gregg Kellogg\" .","When processing a JSON-LD\n script element,\n the Document Base URL\n of the containing HTML document,\n as defined in [HTML],\n is used to establish the default base IRI of the enclosed\n JSON-LD content.","\n Example 146: Using the document base URL to establish the default base IRI\n ","\n \n \n \n \n","@base .\n@prefix foaf: .\n@prefix schema: .\n@prefix xsd: .\n\n foaf:name \"John Lennon\";\n schema:birthDate \"1940-10-09\"^^xsd:date;\n schema:spouse .","HTML allows for Dynamic changes to base URLs.\n This specification does not require any specific behavior,\n and to ensure that all systems process the base IRI equivalently, authors SHOULD\n either use IRIs, or explicitly as defined in § 4.1.3 Base IRI.\n Implementations (particularly those natively operating in the [DOM]) MAY take into consideration\n Dynamic changes to base URLs.","Due to the HTML ","Restrictions for contents of ","","[{\n \"@type\": [\"http://schema.org/WebPageElement\"],\n \"http://schema.org/name\": [{\"@value\": \"Encoding Issues\"}],\n \"http://schema.org/description\": [\n {\"@value\": \"Issues list such as unescaped </script> or -->\"}\n ]\n}]","@prefix schema: .\n\n[ a schema:WebPageElement;\n schema:name \"Encoding Issues\";\n schema:description \"Issues list such as unescaped </script> or -->\"\n] .","7.3 Locating a Specific JSON-LD Script Element","A specific\n script element\n within an HTML document may be located using\n a fragment identifier matching the unique identifier\n of the script element within the HTML document located by a URL (see [DOM]).\n A JSON-LD processorMUST extract only the specified data block's contents\n parsing it as a standalone JSON-LD document\n and MUST NOT merge the result with any other markup from the same HTML document.","For example, given an HTML document located at ","http://example.com/document",",\n a script element identified by \"dave\" can be targeted using the URL\n ","http://example.com/document#dave","\n Example 148: Targeting a specific script element by id\n ","Targeting a script element with id \"gregg\"","
Data describing Dave
\n\n\n
Data describing Gregg
\n","@prefix schema: .\n\n a schema:Person;\n schema:name \"Gregg Kellogg\" .","8. Data Model","JSON-LD is a serialization format for Linked Data based on JSON.\n It is therefore important to distinguish between the syntax, which is\n defined by JSON in [RFC8259], and the data model which is\n an extension of the RDF data model [RDF11-CONCEPTS].\n The precise details of how JSON-LD relates to the RDF data model are given in\n § 10. Relationship to RDF.","To ease understanding for developers unfamiliar with the RDF model, the\n following summary is provided:","A JSON-LD document serializes a\n RDF Dataset\n [RDF11-CONCEPTS], which is a collection of graphs\n that comprises exactly one default graph\n and zero or more named graphs.\n ","The default graph does not have a name and MAY be empty.","Each named graph is a pair consisting of an IRI or\n blank node identifier (the\n graph name)\n and a graph. Whenever practical, the graph nameSHOULD be an IRI.","A graph\n is a labeled directed graph, i.e., a set of nodes\n connected by directed-arcs.","Every directed-arc is labeled with\n an ",". Within the JSON-LD syntax\n these arc labels are called ",".\n Whenever practical, a directed-arc "," be labeled with an "," to label properties is obsolete,\n and may be removed in a future version of JSON-LD.\n Consider using a document-relative ",", instead, such as ","Every node\n is an IRI, a blank node, or a literal,\n although syntactically lists and native JSON values may be represented directly.","A node having an outgoing edge MUST be an IRI or a\n blank node."," contain unconnected ",",\n i.e., nodes which are not connected by an "," to any other ","\n Example 149: Illegal Unconnected Node\n ","{\n \"@id\": \"http://example.org/1\"\n}","\n This effectively just prohibits unnested, empty ","\n and unnested "," that contain only an ",".\n A document may have "," which are unrelated, as long as one or more\n properties are defined, or the "," is referenced from another ","An IRI (Internationalized Resource Identifier) is a string that conforms to the syntax\n defined in [RFC3987]. IRIs used within a\n graphSHOULD return a Linked Data document describing\n the resource denoted by that IRI when being dereferenced.","A blank node is a node which is neither an IRI,\n nor a JSON-LD value, nor a list. A blank node is identified\n using a blank node identifier.","\n is a string that can be used as an identifier for a "," within\n the scope of a ",". Blank node identifiers begin with\n "," (which is interpreted\n as a "," with type ","xsd:string","), a ","\n (","numbers"," with a non-zero fractional part, i.e., the result of a modulo‑1 operation,\n ","or which are too large to represent as integers\n (see Data Round Tripping) in [JSON-LD11-API]),","\n are interpreted as ","xsd:double",", all other\n "," are interpreted as ","\n with type ","), "," (which are interpreted as\n ","xsd:boolean","),\n or a ","A typed value consists of a value, which is a string, and a type, which is an\n IRI.","A language-tagged string\n consists of a string and a non-empty language tag as defined by [BCP47].\n The language tag MUST be well-formed according to section\n 2.2.9 Classes of Conformance\n of [BCP47].\n Processors MAY normalize language tags to lowercase.\n ","Either strings, or language-tagged strings may include\n a base direction, which represents an extension to the underlying\n RDF data model.","A list is a sequence of zero or more IRIs,\n blank nodes, and JSON-LD values.\n Lists are interpreted as\n RDF list structures [RDF11-MT].","JSON-LD documentsMAY contain data\n that cannot be represented by the data model\n defined above. Unless otherwise specified, such data is ignored when a\n JSON-LD document is being processed. One result of this rule\n is that properties which are not mapped to an IRI,\n a blank node, or keyword will be ignored.","Additionally, the JSON serialization format is internally represented using\n the JSON-LD internal representation, which uses the generic\n concepts of lists, maps,\n strings, numbers, booleans, and null to describe\n the data represented by a JSON document.","The image depicts a linked data dataset with a default graph\n and two named graphs.","Figure 1 An illustration of a linked data dataset. \n A description of the linked data dataset\n diagram is available in the Appendix. Image available in\n \n SVG\n and\n \n PNG\n \n formats.","The dataset described in this figure can be represented as follows:","\n Example 150: Linked Data Dataset\n ","{\n \"@context\": [\n \"http://schema.org/\",\n {\"@base\": \"http://example.com/\"}\n ],\n \"@graph\": [{\n \"@id\": \"people/alice\",\n \"gender\": [\n {\"@value\": \"weiblich\", \"@language\": \"de\"},\n {\"@value\": \"female\", \"@language\": \"en\"}\n ],\n \"knows\": {\"@id\": \"people/bob\"},\n \"name\": \"Alice\"\n }, {\n \"@id\": \"graphs/1\",\n \"@graph\": {\n \"@id\": \"people/alice\",\n \"parent\": {\n \"@id\": \"people/bob\",\n \"name\": \"Bob\"\n }\n }\n }, {\n \"@id\": \"graphs/2\",\n \"@graph\": {\n \"@id\": \"people/bob\",\n \"sibling\": {\n \"name\": \"Mary\",\n \"sibling\": {\"@id\": \"people/bob\"}\n }\n }\n }]\n}","[{\n \"@id\": \"http://example.com/people/alice\",\n \"http://schema.org/name\": [{\"@value\": \"Alice\"}],\n \"http://schema.org/gender\": [\n {\"@value\": \"weiblich\",\"@language\": \"de\"},\n {\"@value\": \"female\",\"@language\": \"en\"}\n ],\n \"http://schema.org/knows\": [\n {\"@id\": \"http://example.com/people/bob\"}\n ]\n}, {\n \"@id\": \"http://example.com/graphs/1\",\n \"@graph\": [{\n \"@id\": \"http://example.com/people/alice\",\n \"http://schema.org/parent\": [{\n \"@id\": \"http://example.com/people/bob\",\n \"http://schema.org/name\": [{\"@value\": \"Bob\"}]\n }]\n }]\n}, {\n \"@id\": \"http://example.com/graphs/2\",\n \"@graph\": [{\n \"@id\": \"http://example.com/people/bob\",\n \"http://schema.org/sibling\": [{\n \"http://schema.org/name\": [{\"@value\": \"Mary\"}],\n \"http://schema.org/sibling\": [\n {\"@id\": \"http://example.com/people/bob\"}\n ]\n }]\n }]\n}]","http://example.com/people/alice","Alice","schema:gender","weiblich","female","http://example.com/people/bob","http://example.com/graphs/1","Bob","schema:parent","http://example.com/graphs/2","schema:sibling","Mary","@prefix schema: .\n\n schema:knows ;\n schema:name \"Alice\";\n schema:gender \"weiblich\"@de, \"female\"@en .\n\n {\n schema:parent .\n schema:name \"Bob\" .\n}\n\n {\n schema:sibling [\n schema:name \"Mary\";\n schema:sibling \n ] .\n}","Note the use of "," at the outer-most level to describe three top-level\n resources (two of them ","). The named graphs use "," in addition\n to "," to provide the name for each graph.","9. JSON-LD Grammar","This section restates the syntactic conventions described in the\n previous sections more formally.","A JSON-LD documentMUST be valid JSON text as described\n in [RFC8259], or some format that can be represented\n in the JSON-LD internal representation that is equivalent to\n valid JSON text."," be a single "," consisting of only\n the "," and/or ",",\n or an "," of zero or more ","In contrast to JSON, in JSON-LD the keys in objects\n MUST be unique.","Whenever a keyword is discussed in this grammar,\n the statements also apply to an alias for that keyword."," to be aliased\n (see ","§ 4.1.6 Aliasing Keywords"," for details). For example, if the ","\n defines the "," as an alias for ",",\n that alias may be legitimately used as a substitution for "," aliases are not expanded during context\n processing.","9.1 Terms","A term is a short-hand string that expands\n to an IRI, blank node identifier, or keyword."," equal any of the JSON-LD ","other than ","When used as the ","Compact IRI",", to avoid\n the potential ambiguity of a "," being confused with an ","\n scheme, "," come from the list of URI schemes as defined in\n [","IANA-URI-SCHEMES","]. Similarly, to avoid confusion between a\n ",", terms "," include a colon (",")\n and "," be restricted to the form of\n ","isegment-nz-nc","\n as defined in [","To avoid forward-compatibility issues, a "," start\n with an "," character\n ","\n as future versions of JSON-LD may introduce\n additional ",". Furthermore, the term ","\n be an empty ",") as not all programming languages\n are able to handle empty JSON keys.","See § 3.1 The Context and\n § 3.2 IRIs for further discussion\n on mapping terms to IRIs.","9.2 Node Objects","A node object represents zero or more properties of a\n node in the graph serialized by the\n JSON-LD document. A map is a\n node object if it exists outside of a JSON-LD\n context and:"," in the JSON-LD document consisting\n of no other ",",\n or "," keywords, and","it is not a graph object.","The properties of a node in\n a graph may be spread among different\n node objects within a document. When\n that happens, the keys of the different\n node objects need to be merged to create the\n properties of the resulting node.","A node objectMUST be a map. All keys\n which are not IRIs, compact IRIs, terms valid in the\n active context, or one of the following keywords\n (or alias of such a keyword)\n MUST be ignored when processed:",", or","If the "," contains the ","\n key, its value "," be ",",\n a ",", or\n an "," composed of any of these."," key,\n its value "," be an ",",\n or a "," (including\n ",").\n See ","§ 4.1.5 Compact IRIs",", and\n ","§ 4.5.1 Identifying Blank Nodes"," for further discussion on\n "," values."," be\n a "," or\n an ",".\n If the "," also contains an "," keyword,\n its value is used as the ",".\n See "," values. As a special case, if a ","\n contains no keys other than ",", and the\n "," is the root of the JSON-LD document, the\n "," is not treated as a ","; this\n is used as a way of defining ","\n that may not form a connected graph. This allows a\n "," to be defined which is shared by all of the constituent\n "," be either an ","\n (including ","),\n a "," expanding into an "," of any of these.\n See "," be a "," containing "," representing reverse\n properties. Each value of such a reverse property "," containing a combination of these.","§ 9.13 Included Blocks"," for further discussion\n on ","included blocks",". See\n ","\n which "," include a ","§ 9.14 Property Nesting","Keys in a node object that are not\n keywordsMAY expand to an IRI\n using the active context. The values associated with keys that expand\n to an IRIMUST be one of the following:","string,","number,","null,","node object,","graph object,","value object,","list object,","set object,","an array of zero or more of any of the possibilities above,","a language map,","an index map,","an included block","an id map, or","a type map","9.3 Frame Objects","When framing, a frame object extends a node object to allow\n entries used specifically for framing."," as the value of any key\n which is not a ",".\n Values of "," include the value ","@null",",\n or an "," containing only ",", in addition to other values\n allowed in the grammar for values of "," keys expanding to "," additionally be\n an empty ","wildcard","),\n an "," containing only an empty ",",\n an empty ","match none",")\n an "," include an ","@embed"," with\n any value from ","@always","@once","@never"," include "," with the boolean valued\n keys ","@explicit","@omitDefault","@requireAll","In addition to other property values, a property of a frame object\n MAY include a value pattern\n (See § 9.6 Value Patterns).","See [JSON-LD11-FRAMING] for a description of how frame objects are used.","9.4 Graph Objects",", which "," include\n an explicit ",".\n A "," if\n it exists outside of a JSON-LD ",",\n it contains an "," (or an alias of that ","),\n it is not the top-most "," in the JSON-LD document, and\n it consists of no "," other than ","\n and ",", or an alias of one of these "," key,\n its value is used as the identifier (",") of a "," without an "," is also a\n "," and represents a "," without an\n explicit identifier, although in the data model it still has a\n ",", which is an implicitly allocated\n ","The value of the "," key "," values..","9.5 Value Objects","A value object is used to explicitly associate a type or a\n language with a value to create a typed value or a language-tagged string\n and possibly associate a base direction."," containing the\n "," key. It "," also contain an ",",\n an ","an ","\n an ",", or an "," key but "," contain\n both an "," and either ","or ","\n keys at the same time.\n A "," contain any other keys that expand to an\n ","The value associated with the "," be either a\n ","If the value associated with the "," key","\n is ",", the value "," be a\n ",",\n a string which can be turned into an ",",\n or "," have the\n ","lexical form"," described in [","], or be "," be\n one of ",", or be ","See § 4.2.1 Typed Values and\n § 4.2.4 String Internationalization\n for more information on value objects.","9.6 Value Patterns","When framing,\n a value pattern\n extends a value object to allow\n entries used specifically for framing.","The values of\n ",",\n "," and\n ","9.7 Lists and Sets"," represents an ","ordered"," set of values. A set\n represents an ","unordered"," set of values. Unless otherwise specified,\n ","arrays"," are unordered in JSON-LD. As such, the\n "," keyword, when used in the body of a JSON-LD document,\n represents just syntactic sugar which is optimized away when processing the document.\n However, it is very helpful when used within the context of a document. Values\n of terms associated with an "," container\n will always be represented in the form of an "," when a document\n is processed—even if there is just a single value that would otherwise be optimized to\n a non-array form in ",".\n This simplifies post-processing of the data as the data is always in a\n deterministic form."," that contains no\n keys that expand to an "," other\n than ",".\n Please note that the "," key will be ignored when being processed.","In both cases, the value associated with the keys "," be one of the following types:","value object, or","an array of zero or more of the above possibilities","See § 4.3 Value Ordering for further discussion on sets and lists.","9.8 Language Maps"," is used to associate a language with a value in a\n way that allows easy programmatic access. A "," may be\n used as a term value within a "," if the "," is defined\n with ","\n or an array containing both ",". The keys of a\n "," representing\n [","] language tags, the "," which expands to ",",\n and the values "," be any of the following types:","string, or","an array of zero or more of the strings","See § 4.2.4 String Internationalization for further discussion\n on language maps.","9.9 Index Maps"," allows keys that have no semantic meaning,\n but should be preserved regardless, to be used in JSON-LD documents.\n An "," may\n be used as a "," value within a "," if the\n term is defined with ",".\n The values of the "," of an "," be one\n of the following types:","See § 4.6.1 Data Indexing for further information on this topic."," may also be used to map indexes to associated\n ",", if the term is defined with ","\n set to an array containing both "," and\n ",", and optionally including ",". The\n value consists of the "," contained within the ","named\n graph"," which is indexed using the referencing key, which can be\n represented as a "," if the value does\n not include ",", or a "," if it includes ","9.10 Property-based Index Maps","A property-based "," is a variant of ","\n were indexes are semantically preserved in the graph as property values.\n A property-based "," may be used as a term value within a ","\n if the "," is defined with ",",\n or an array containing both ",",\n and with "," set to a ",".\n The values of a property-based ","\n or "," which expand to ","When expanding,\n if the "," contains a ","\n for the value of ",",\n this "," will be used to expand the keys of the ",".\n Otherwise, the keys will be expanded as simple ",".\n Each "," in the expanded values of the ","\n will be added an additional property value,\n where the property is the expanded value of ",",\n and the value is the expanded referencing key.\n ","See § 4.6.1.1 Property-based data indexing for further information on this topic.","9.11 Id Maps"," is used to associate an "," with a value that allows easy\n programmatic access. An ","\n is defined with ",".\n The keys of an ","IRI references"," (including ",")),\n the ","If the value contains a property expanding to ",", its value ","\n be equivalent to the referencing key. Otherwise, the property from the value is used as\n the "," value when expanding."," may also be used to map ","graph names"," to their\n ",",\n and optionally including ",". The value consists of the\n ","\n which is named using the referencing key.","9.12 Type Maps"," with a value that allows easy\n programmatic access. A ",".\n The keys of a ",")),\n ",",\n or the ",", and its value\n is contains the referencing key after suitable expansion of both the referencing key\n and the value, then the "," already contains the type. Otherwise, the property from the value is\n added as a ","9.13 Included Blocks"," is used to provide a set of ",".\n An "," appear as the value of a member of a node object with either the key of "," is either a "," or an array of ","When expanding, multiple included blocks will be coalesced into a single included block.","9.14 Property Nesting","A nested property is used to gather properties of a node object in a separate\n map, or array of maps which are not\n value objects. It is semantically transparent and is removed\n during the process of expansion. Property nesting is recursive, and\n collections of nested properties may contain further nesting.","Semantically, nesting is treated as if the properties and values were declared directly\n within the containing node object.","9.15 Context Definitions","A context definition defines a local context in a\n node object."," whose\n keys "," be either ",",\n or one of the ",",\n or "," has an "," key,\n its value "," be one of ",".\n When used as a reference from an ",", the referenced ","\n include an "," key, itself."," have the ","] or be "," with only the ",",\n and optionally an entry ","The value of keys that are not keywordsMUST be either an\n IRI, a compact IRI, a term,\n a blank node identifier, a keyword, null,\n or an expanded term definition.","9.15.1 Expanded term definition","An expanded term definition is used to describe the mapping\n between a term and its expanded identifier, as well as other\n properties of the value associated with the term when it is\n used as key in a node object.","\n composed of zero or more keys from\n ",", or\n "," contain any other keys.","When the associated term is "," contain keys other than ",".\n The value of "," is limited to the single value ","If the term being defined is not an ","\n and the "," does not have an\n "," mapping, the ","\n include the ","Term definitions with keys which are of the form of an IRI or a compact IRIMUST NOT\n expand to an IRI other than the expansion of the key itself.","If an ",",\n it "," have "," at the same time,\n its value ",". If an\n "," exists, its value ",", a\n ",", or one of the\n ",",\n its value "," be either\n ",", or be\n ","\n or an "," containing exactly any one of those keywords, or a\n combination of "," and any of "," in any order\n "," may also be an array\n containing "," along with either "," and also optionally including ","\n If the value\n is ",", when the "," is used outside of the\n ",", the associated value ",".\n If the value is "," is used outside of\n the "," be an\n "," be a valid ",", or a term\n which expands to ","TermsMUST NOT be used in a circular manner. That is,\n the definition of a term cannot depend on the definition of another term if that other\n term also depends on the first term.","See § 3.1 The Context for further discussion on contexts.","9.16 Keywords","JSON-LD keywords are described in § 1.7 Syntax Tokens and Keywords,\n this section describes where each keyword may appear within different JSON-LD structures.","Within\n ","list objects","set objects",", and\n "," aliases "," be used instead of the corresponding ",", except for "," be aliased.\n Within "," NOT used.","\n The unaliased "," keyword "," be used as a key in a ",".\n Its value "," be used as a key in an ","or an "," in any order.\n The value may also be an array\n containing ","\n The "," be aliased, and "," be used as a key in the following objects:\n ","node objects (see § 9.2 Node Objects),","value objects (see § 9.5 Value Objects),","graph objects (see § 9.4 Graph Objects),","list objects (see § 9.7 Lists and Sets),","set objects (see § 9.7 Lists and Sets),","nested properties (see § 9.14 Property Nesting), and","expanded term definitions (see § 9.15 Context Definitions).","\n The value of "," be\n "," composed of any of these.\n "," be aliased and ","The unaliased ","See § 4.2.4.1 Base Direction for a further discussion.",",\n where its value ",", or an array of either "," be used as the value of the "," key within an ","See § 4.9 Named Graphs.",",\n or as the value of the "," be an ",",\n or a ","See ",", and\n "," for further discussion on\n "," be used in a ","§ 4.1.10 Imported Contexts"," for a further discussion.\n "," be aliased and\n its value ",".\n This keyword is described further in ","§ 4.7 Included Nodes",",\n and "," be used as a key in a\n ","\n and as an entry in a ",", where the value an ",",\n a ","See § 9.9 Index Maps, and\n § 4.6.1.1 Property-based data indexing for a further discussion."," be aliased\n and "," key within a ","\n or an ","See § 4.2.2 JSON Literals.","See § 4.2.4 String Internationalization, § 9.8 Language Maps.",".\n The unaliased "," be one of the following:\n ",",\n where its value must be a "," be used as the value of a ",",\n or as a key in an ",",\n where its value "," be a string expanding to ","See § 9.14 Property Nesting for a further discussion."," be used as a key in an\n ","§ 4.6.2 Language Indexing","§ 4.9.3 Named Graph Indexing","\n for a further discussion.","\n for a further discussion.\n ",",\n or an ","See § 4.8 Reverse Properties and\n § 9.15 Context Definitions for further discussion.",").\n ",",\n where its value may also be either ","Within a context, "," may be used as the key for an ",",\n whose entries are limited to ","This keyword is described further in § 3.5 Specifying the Type\n and § 4.2.1 Typed Values.",".\n Its value key "," be either a ","§ 9.5 Value Objects","\n or as the value of "," in an ","10. Relationship to RDF","JSON-LD is a\n concrete RDF syntax\n as described in [RDF11-CONCEPTS]. Hence, a JSON-LD document is both an\n RDF document and a JSON document and correspondingly represents an\n instance of an RDF data model. However, JSON-LD also extends the RDF data\n model to optionally allow JSON-LD to serialize\n generalized RDF Datasets.\n The JSON-LD extensions to the RDF data model are:","In JSON-LD properties can be\n IRIs or blank nodes\n whereas in RDF properties (predicates) have to be IRIs. This\n means that JSON-LD serializes\n generalized RDF Datasets.","In JSON-LD lists use native JSON syntax, either contained in a\n list object, or described as such within a context. Consequently, developers\n using the JSON representation can access list elements directly rather than\n using the vocabulary for collections described in [RDF-SCHEMA].","RDF values are either typed ","literals",") or\n ","language-tagged strings"," whereas\n JSON-LD also supports JSON's native data types, i.e., ",", and the boolean values ",". The JSON-LD 1.1 Processing Algorithms and API specification [","]\n defines the ","conversion rules","\n between JSON's native data types and RDF's counterparts to allow round-tripping.","As an extension to the RDF data model,\n literals without an explicit datatype\n MAY include a base direction.\n As there is currently no standardized mechanism for representing the base direction\n of RDF literals, the JSON-LD to standard RDF transformation loses the base direction.\n However, the Deserialize JSON-LD to RDF Algorithm\n provides a means of representing base direction\n using mechanisms which will preserve round-tripping through non-standard RDF.","The use of blank node identifiers to label properties is obsolete,\n and may be removed in a future version of JSON-LD, as is the support for generalized RDF Datasets.","Summarized, these differences mean that JSON-LD is capable of serializing any RDF\n graph or dataset and most, but not all, JSON-LD documents can be directly\n interpreted as RDF as described in RDF 1.1 Concepts [RDF11-CONCEPTS].","Authors are strongly encouraged to avoid labeling properties using blank node identifiers,\n instead, consider one of the following mechanisms:","a relative IRI reference, either relative to the document or the vocabulary\n (see § 4.1.4 Using the Document Base for the Default Vocabulary for a discussion on using the document base as part of the vocabulary mapping),","a URN such as ","urn:example:1",", see [","], or","a \"Skolem IRI\" as per\n Replacing Blank Nodes with IRIs\n of [RDF11-CONCEPTS].","The normative algorithms for interpreting JSON-LD as RDF and serializing\n RDF as JSON-LD are specified in the JSON-LD 1.1 Processing Algorithms and API\n specification [JSON-LD11-API].","Even though JSON-LD serializes\n RDF Datasets, it can\n also be used as a graph source.\n In that case, a consumer MUST only use the default graph and ignore all named graphs.\n This allows servers to expose data in languages such as Turtle and JSON-LD\n using HTTP content negotiation.","Publishers supporting both dataset and graph syntaxes have to ensure that\n the primary data is stored in the default graph to enable consumers that do not support\n datasets to process the information.","10.1 Serializing/Deserializing RDF","The process of serializing RDF as JSON-LD and deserializing JSON-LD to RDF\n depends on executing the algorithms defined in\n RDF Serialization-Deserialization Algorithms\n in the JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API].\n It is beyond the scope of this document to detail these algorithms any further,\n but a summary of the necessary operations is provided to illustrate the process.","The procedure to deserialize a JSON-LD document to RDF involves the\n following steps:","Expand the JSON-LD document, removing any context; this ensures\n that properties, types, and values are given their full representation\n as IRIs and expanded values. Expansion\n is discussed further in § 5.1 Expanded Document Form.","Flatten the document, which turns the document into an array of\n node objects. Flattening is discussed\n further in § 5.3 Flattened Document Form.","Turn each node object into a series of triples.","For example, consider the following JSON-LD document in compact form:","\n Example 151: Sample JSON-LD document\n ","{\n \"@context\": {\n \"name\": \"http://xmlns.com/foaf/0.1/name\",\n \"knows\": \"http://xmlns.com/foaf/0.1/knows\"\n },\n \"@id\": \"http://me.markus-lanthaler.com/\",\n \"name\": \"Markus Lanthaler\",\n \"knows\": [\n {\n \"@id\": \"http://manu.sporny.org/about#manu\",\n \"name\": \"Manu Sporny\"\n }, {\n \"name\": \"Dave Longley\"\n }\n ]\n}","Running the JSON-LD Expansion and Flattening algorithms against the\n JSON-LD input document in the example above would result in the\n following output:","\n Example 152: Flattened and expanded form for the previous example\n ","[\n {\n \"@id\": \"_:b0\",\n \"http://xmlns.com/foaf/0.1/name\": \"Dave Longley\"\n }, {\n \"@id\": \"http://manu.sporny.org/about#manu\",\n \"http://xmlns.com/foaf/0.1/name\": \"Manu Sporny\"\n }, {\n \"@id\": \"http://me.markus-lanthaler.com/\",\n \"http://xmlns.com/foaf/0.1/name\": \"Markus Lanthaler\",\n \"http://xmlns.com/foaf/0.1/knows\": [\n { \"@id\": \"http://manu.sporny.org/about#manu\" },\n { \"@id\": \"_:b0\" }\n ]\n }\n]","Deserializing this to RDF now is a straightforward process of turning\n each node object into one or more triples. This can be\n expressed in Turtle as follows:","\n Example 153: Turtle representation of expanded/flattened document\n ","@prefix foaf: <http://xmlns.com/foaf/0.1/> .\n\n_:b0 foaf:name \"Dave Longley\" .\n\n//manu.sporny.org/about#manu> foaf:name \"Manu Sporny\" .\n\n<http://me.markus-lanthaler.com/> foaf:name \"Markus Lanthaler\" ;\n foaf:knows //manu.sporny.org/about#manu>, _:b0 .","The process of serializing RDF as JSON-LD can be thought of as the\n inverse of this last step, creating an expanded JSON-LD document closely\n matching the triples from RDF, using a single node object\n for all triples having a common subject, and a single property\n for those triples also having a common predicate. The result may\n then be framed by using the\n Framing Algorithm\n described in [JSON-LD11-FRAMING] to create the desired object embedding.","RDF provides for JSON content as a possible ","literal value",".\n This allows markup in literal values.\n Such content is indicated in a "," using a "," whose datatype is set to "," datatype is defined as follows:","The IRI denoting this datatype","is ","http://www.w3.org/1999/02/22-rdf-syntax-ns#JSON","The lexical space","is the set of UNICODE [UNICODE] strings which conform to the JSON Grammar\n as described in Section 2 JSON Grammar of [RFC8259].","The value space","is the set of UNICODE [","UNICODE","] strings which conform to the ","JSON Grammar","\n as described in ","Section 2 JSON Grammar"," of [","],\n and furthermore comply with the following constraints:\n ","It MUST NOT contain any unnecessary whitespace,","Keys in objects MUST be ordered lexicographically,","Native Numeric values MUST be serialized according to\n Section 7.1.12.1 of [ECMASCRIPT],","Strings "," be serialized with Unicode codepoints from ","U+0000"," through ","U+001F","\n using lower case hexadecimal Unicode notation (","\\uhhhh",") unless in the set\n of predefined JSON control characters ","U+0008","U+0009",",\n ","U+000A","U+000C","U+000D","\n which "," be serialized as ","\\b","\\t","\\n","\\f","\\r"," respectively.\n All other Unicode characters "," be serialized \"as is\", other than\n ","U+005C","\\",") and ","U+0022","\"",")\n which ","\\\\","\\\""," respectively.","Issue","The JSON Canonicalization Scheme (JCS) [RFC8785]\n is an emerging standard for JSON canonicalization.\n This specification will likely be updated to require such a canonical representation.\n Users are cautioned from depending on the\n JSON literal lexical representation as an RDF literal,\n as the specifics of serialization may change in a future revision of this document.","\n Despite being defined as a set of strings,\n this value space is considered distinct from the value space of ",",\n in order to avoid side effects with existing specifications.\n ","The lexical-to-value mapping","maps any element of the lexical space to the result of\n ","parsing it into\n an internal representation consistent with [","ECMASCRIPT","] representation\n created by using the ","JSON.parse"," function as defined in\n ","Section 24.5 The JSON Object","],","then serializing it in the JSON format [RFC8259]\n in compliance with the constraints of the value space described above.\n ","The canonical mapping","maps any element of the value space to the identical string in the lexical space."," namespace is used for describing combinations of "," in ","RDF literals",".\n It is used as an alternative mechanism for describing the [","] ","\n of "," that would otherwise use the "," datatypes.","Datatypes based on this namespace allow round-tripping of JSON-LD documents using base direction,\n although the mechanism is not otherwise standardized.","\n can be used with the ","rdfDirection"," option\n set to ","i18n-datatype"," to generate "," base to create an ","\n encoding the "," along with optional "," (normalized to lower case)\n from value objects containing "," by appending to ","\n the value of ",", if any, followed by an underscore (","\"_\"",") followed\n by the value of ","For improved interoperability, the language tag is normalized to\n lower case when creating the datatype IRI.","The following example shows two statements with literal values of ","i18n:ar-EG_rtl",",\n which encodes the language tag "," and the base direction ","@prefix ex: .\n@prefix i18n: .\n\n# Note that this version preserves the base direction using a non-standard datatype.\n[\n ex:title \"HTML و CSS: تصميم و إنشاء مواقع الويب\"^^i18n:ar-eg_rtl;\n ex:publisher \"مكتبة\"^^i18n:ar-eg_rtl\n] .","See § 4.2.4.1 Base Direction for more details\n on using base direction for strings.","This specification defines the "," class, which is in the domain\n of "," to be used for describing RDF literal values\n containing base direction and a possible language tag to be associated with the\n string value of ","rdf:value"," on the same subject.","A class representing a compound literal.","An RDF ",".\n The range of the property is an ","rdfs:Literal",", whose value "," be a well-formed [",".\n The domain of the property is ","compound-literal"," using these properties to\n describe the "," and optional "," and optionally ","The following example shows two statements with compound literals\n representing strings with the ","@prefix ex: .\n\n# Note that this version preserves the base direction using a bnode structure.\n[\n ex:title [\n rdf:value \"HTML و CSS: تصميم و إنشاء مواقع الويب\",\n rdf:language \"ar-eg\",\n rdf:direction \"rtl\"\n ];\n ex:publisher [\n rdf:value \"مكتبة\",\n rdf:language \"ar-eg\",\n rdf:direction \"rtl\"\n ]\n] .","11. Security Considerations","See, Security Considerations in § C. IANA Considerations.","Future versions of this specification\n may incorporate subresource integrity [SRI] as a means of ensuring that cached and retrieved\n content matches data retrieved from remote servers; see issue 86.","12. Privacy Considerations","The retrieval of external contexts can expose the operation of a JSON-LD processor,\n allow intermediate nodes to fingerprint the client application through introspection of retrieved resources\n (see [fingerprinting-guidance]),\n and provide an opportunity for a man-in-the-middle attack.\n To protect against this, publishers should consider caching remote contexts for future use,\n or use the documentLoader\n to maintain a local version of such contexts.","13. Internationalization Considerations","As JSON-LD uses the RDF data model, it is restricted by design in its ability to\n properly record JSON-LD Values which are strings with left-to-right or right-to-left direction indicators.\n Both JSON-LD and RDF provide a mechanism for specifying the language associated with\n a string (language-tagged string), but do not provide a means of indicating\n the base direction of the string.","Unicode provides a mechanism for signaling direction within a string\n (see Unicode Bidirectional Algorithm [UAX9]),\n however, when a string has an overall base direction which cannot be determined by the\n beginning of the string, an external indicator is required,\n such as the [HTML] dir attribute,\n which currently has no counterpart for RDF literals.","The issue of properly representing base direction in RDF is not something that\n this Working Group can handle, as it is a limitation or the core RDF data model.\n This Working Group expects that a future RDF Working Group will consider the matter\n and add the ability to specify the base direction of language-tagged strings.","Until a more comprehensive solution can be addressed in a future version of this\n specification, publishers should consider this issue when representing strings\n where the base direction of the string cannot otherwise be correctly inferred\n based on the content of the string.\n See [string-meta] for a discussion best practices for\n identifying language and base direction for strings used on the Web.","A. Image Descriptions","A.1 Linked Data Dataset","This section describes the Linked Data Dataset figure in § 8. Data Model.","The image consists of three dashed boxes, each describing a different\n linked data graph. Each box consists of shapes linked with arrows describing\n the linked data relationships.","The first box is titled \"default graph: \" describes two\n resources: ","\n (denoting \"Alice\" and \"Bob\" respectively), which are\n connected by an arrow labeled "," which describes\n the knows relationship between the two resources. Additionally, the \"Alice\" resource is related\n to three different literals:","an RDF literal with no datatype or language.","weiblich | de","an language-tagged string with the value \"weiblich\" and language tag \"de\".","female | en","an language-tagged string with the value \"female\" and language tag \"en\".","The second and third boxes describe two named graphs, with the graph names\n \"http://example.com/graphs/1\" and \"http://example.com/graphs/1\", respectively.","The second box consists of two resources:\n ","\n related by the "," relationship, and names the\n "," \"Bob\".","The third box consists of two resources, one\n named "," and the other unnamed.\n The two resources related to each other using "," relationship\n with the second named \"Mary\".","B. Relationship to Other Linked Data Formats","The JSON-LD examples below demonstrate how JSON-LD can be used to\n express semantic data marked up in other linked data formats such as Turtle,\n RDFa, and Microdata. These sections are merely provided as\n evidence that JSON-LD is very flexible in what it can express across different\n Linked Data approaches.","B.1 Turtle","The following are examples of transforming RDF expressed in [Turtle]\n into JSON-LD.","B.1.1 Prefix definitions","The JSON-LD context has direct equivalents for the Turtle\n "," declaration:","\n Example 154: A set of statements serialized in Turtle\n ","@prefix foaf: <http://xmlns.com/foaf/0.1/> .\n\n//manu.sporny.org/about#manu> a foaf:Person;\n foaf:name \"Manu Sporny\";\n foaf:homepage //manu.sporny.org/> .","\n Example 155: The same set of statements serialized in JSON-LD\n ","{\n \"@context\": {\n \"foaf\": \"http://xmlns.com/foaf/0.1/\"\n },\n \"@id\": \"http://manu.sporny.org/about#manu\",\n \"@type\": \"foaf:Person\",\n \"foaf:name\": \"Manu Sporny\",\n \"foaf:homepage\": { \"@id\": \"http://manu.sporny.org/\" }\n}","B.1.2 Embedding","Both [Turtle] and JSON-LD allow embedding, although [Turtle] only allows embedding of\n blank nodes.","\n Example 156: Embedding in Turtle\n ","@prefixfoaf: <http://xmlns.com/foaf/0.1/> .\n\n<http://manu.sporny.org/about#manu>\n a foaf:Person;\n foaf:name \"ManuSporny\";\n foaf:knows[ a foaf:Person; foaf:name \"Gregg Kellogg\" ] .","\n Example 157: Same embedding example in JSON-LD\n ","{\n \"@context\": {\n \"foaf\": \"http://xmlns.com/foaf/0.1/\"\n },\n \"@id\": \"http://manu.sporny.org/about#manu\",\n \"@type\": \"foaf:Person\",\n \"foaf:name\": \"Manu Sporny\",\n \"foaf:knows\": {\n \"@type\": \"foaf:Person\",\n \"foaf:name\": \"Gregg Kellogg\"\n }\n}","B.1.3 Conversion of native data types","In JSON-LD numbers and boolean values are native data types. While [","]\n has a shorthand syntax to express such values, RDF's abstract syntax requires\n that numbers and boolean values are represented as typed literals. Thus,\n to allow full round-tripping, the JSON-LD 1.1 Processing Algorithms and API specification [","]\n defines conversion rules between JSON-LD's native data types and RDF's\n counterparts. ","Numbers"," without fractions are\n converted to ","-typed literals, numbers with fractions\n to ","-typed literals and the two boolean values\n "," to a ","-typed\n literal. All typed literals are in canonical lexical form.","\n Example 158: JSON-LD using native data types for numbers and boolean values\n ","{\n \"@context\": {\n \"ex\": \"http://example.com/vocab#\"\n },\n \"@id\": \"http://example.com/\",\n \"ex:numbers\": [ 14, 2.78 ],\n \"ex:booleans\": [ true, false ]\n}","\n Example 159: Same example in Turtle using typed literals\n ","@prefixex: <http://example.com/vocab#> .\n@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .\n\n<http://example.com/>\n ex:numbers \"14\"^^xsd:integer, \"2.78E0\"^^xsd:double ;\n ex:booleans \"true\"^^xsd:boolean, \"false\"^^xsd:boolean .","Note that this interpretation differs from [","],\n in which the literal ","2.78"," translates to an ",".\n The rationale is that most JSON tools parse numbers with fractions as\n ","floating point numbers",",\n so "," is the most appropriate datatype to render them back in RDF.\n ","B.1.4 Lists","Both JSON-LD and [Turtle] can represent sequential lists of values.","\n Example 160: A list of values in Turtle\n ","@prefixfoaf: <http://xmlns.com/foaf/0.1/> .\n\n<http://example.org/people#joebob> a foaf:Person;\n foaf:name \"JoeBob\";\n foaf:nick ( \"joe\" \"bob\" \"jaybee\" ) .","\n Example 161: Same example with a list of values in JSON-LD\n ","{\n \"@context\": {\n \"foaf\": \"http://xmlns.com/foaf/0.1/\"\n },\n \"@id\": \"http://example.org/people#joebob\",\n \"@type\": \"foaf:Person\",\n \"foaf:name\": \"Joe Bob\",\n \"foaf:nick\": {\n \"@list\": [ \"joe\", \"bob\", \"jaybee\" ]\n }\n}","B.2 RDFa","The following example describes three people with their respective names and\n homepages in RDFa [RDFA-CORE].","\n Example 162: RDFa fragment that describes three people\n ","
","An example JSON-LD implementation using a single context is\n described below.","\n Example 163: Same description in JSON-LD (context shared among node objects)\n ","{\n \"@context\": {\n \"foaf\": \"http://xmlns.com/foaf/0.1/\",\n \"foaf:homepage\": {\"@type\": \"@id\"}\n },\n \"@graph\": [\n {\n \"@type\": \"foaf:Person\",\n \"foaf:homepage\": \"http://example.com/bob/\",\n \"foaf:name\": \"Bob\"\n }, {\n \"@type\": \"foaf:Person\",\n \"foaf:homepage\": \"http://example.com/eve/\",\n \"foaf:name\": \"Eve\"\n }, {\n \"@type\": \"foaf:Person\",\n \"foaf:homepage\": \"http://example.com/manu/\",\n \"foaf:name\": \"Manu\"\n }\n ]\n}","B.3 Microdata","The HTML Microdata [MICRODATA] example below expresses book information as\n a Microdata Work item.","\n Example 164: HTML that describes a book using microdata\n ","<dlitemscope\n itemtype=\"http://purl.org/vocab/frbr/core#Work\"\n itemid=\"http://purl.oreilly.com/works/45U8QJGZSQKDH8N\">\n <dt>Titledt>\n <dd><citeitemprop=\"http://purl.org/dc/elements/1.1/title\">Just a Geekcite>dd>\n <dt>Bydt>\n <dd><spanitemprop=\"http://purl.org/dc/elements/1.1/creator\">Wil Wheatonspan>dd>\n <dt>Formatdt>\n <dditemprop=\"http://purl.org/vocab/frbr/core#realization\"\n itemscope\n itemtype=\"http://purl.org/vocab/frbr/core#Expression\"\n itemid=\"http://purl.oreilly.com/products/9780596007683.BOOK\">\n <linkitemprop=\"http://purl.org/dc/elements/1.1/type\"href=\"http://purl.oreilly.com/product-types/BOOK\">\n Print\n dd>\n <dditemprop=\"http://purl.org/vocab/frbr/core#realization\"\n itemscope\n itemtype=\"http://purl.org/vocab/frbr/core#Expression\"\n itemid=\"http://purl.oreilly.com/products/9780596802189.EBOOK\">\n <linkitemprop=\"http://purl.org/dc/elements/1.1/type\"href=\"http://purl.oreilly.com/product-types/EBOOK\">\n Ebook\n dd>\ndl>","Note that the JSON-LD representation of the Microdata information stays\n true to the desires of the Microdata community to avoid contexts and\n instead refer to items by their full IRI.","\n Example 165: Same book description in JSON-LD (avoiding contexts)\n ","[\n {\n \"@id\": \"http://purl.oreilly.com/works/45U8QJGZSQKDH8N\",\n \"@type\": \"http://purl.org/vocab/frbr/core#Work\",\n \"http://purl.org/dc/elements/1.1/title\": \"Just a Geek\",\n \"http://purl.org/dc/elements/1.1/creator\": \"Wil Wheaton\",\n \"http://purl.org/vocab/frbr/core#realization\":\n [\n {\"@id\": \"http://purl.oreilly.com/products/9780596007683.BOOK\"},\n {\"@id\": \"http://purl.oreilly.com/products/9780596802189.EBOOK\"}\n ]\n }, {\n \"@id\": \"http://purl.oreilly.com/products/9780596007683.BOOK\",\n \"@type\": \"http://purl.org/vocab/frbr/core#Expression\",\n \"http://purl.org/dc/elements/1.1/type\": {\"@id\": \"http://purl.oreilly.com/product-types/BOOK\"}\n }, {\n \"@id\": \"http://purl.oreilly.com/products/9780596802189.EBOOK\",\n \"@type\": \"http://purl.org/vocab/frbr/core#Expression\",\n \"http://purl.org/dc/elements/1.1/type\": {\"@id\": \"http://purl.oreilly.com/product-types/EBOOK\"}\n }\n]","C. IANA Considerations","This section has been submitted to the Internet Engineering Steering\n Group (IESG) for review, approval, and registration with IANA.","Type name:","application","Subtype name:","ld+json","Required parameters:","N/A","Optional parameters:","A non-empty list of space-separated URIs identifying specific\n constraints or conventions that apply to a JSON-LD document according to [","RFC6906","].\n A profile does not change the semantics of the resource representation\n when processed without profile knowledge, so that clients both with\n and without knowledge of a profiled resource can safely use the same\n representation. The "," parameter "," be used by\n clients to express their preferences in the content negotiation process.\n If the profile parameter is given, a server "," return a document that\n honors the profiles in the list which it recognizes,\n and "," ignore the profiles in the list which it does not recognize.\n It is "," that profile URIs are dereferenceable and provide\n useful documentation at that URI. For more information and background\n please refer to [","This specification defines six values for the "," parameter.","To request or specify expanded JSON-LD document form.","To request or specify compacted JSON-LD document form.","To request or specify a JSON-LD context document.","To request or specify flattened JSON-LD document form.","http://www.w3.org/ns/json-ld#frame","To request or specify a JSON-LD frame document.","To request or specify framed JSON-LD document form.","All other URIs starting with ","http://www.w3.org/ns/json-ld","\n are reserved for future use by JSON-LD specifications.","Other specifications may publish additional "," parameter\n URIs with their own defined semantics.\n This includes the ability to associate a file extension with a ","\n When used as a ","media type parameter","RFC4288","]\n in an ","HTTP Accept header","RFC7231","],\n the value of the "," be enclosed in quotes (",") if it contains\n special characters such as whitespace, which is required when multiple profile URIs are combined.","When processing the \"profile\" media type parameter, it is important to\n note that its value contains one or more URIs and not IRIs. In some cases\n it might therefore be necessary to convert between IRIs and URIs as specified in\n section 3 Relationship between IRIs and URIs\n of [RFC3987].","Encoding considerations:","See RFC 8259, section 11.","Security considerations:","RFC 8259, section 12","]\n ","Since JSON-LD is intended to be a pure data exchange format for\n directed graphs, the serialization "," be passed through a\n code execution mechanism such as JavaScript's ","eval()","\n function to be parsed. An (invalid) document may contain code that,\n when executed, could lead to unexpected side effects compromising\n the security of a system.","When processing JSON-LD documents, links to remote contexts and frames are\n typically followed automatically, resulting in the transfer of files\n without the explicit request of the user for each one. If remote\n contexts are served by third parties, it may allow them to gather\n usage patterns or similar information leading to privacy concerns.\n Specific implementations, such as the API defined in the\n JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API],\n may provide fine-grained mechanisms to control this behavior.","JSON-LD contexts that are loaded from the Web over non-secure connections,\n such as HTTP, run the risk of being altered by an attacker such that\n they may modify the JSON-LD active context in a way that\n could compromise security. It is advised that any application that\n depends on a remote context for mission critical purposes vet and\n cache the remote context before allowing the system to use it.","Given that JSON-LD allows the substitution of long IRIs with short terms,\n JSON-LD documents may expand considerably when processed and, in the worst case,\n the resulting data might consume all of the recipient's resources. Applications\n should treat any data with due skepticism.","As JSON-LD places no limits on the IRI schemes that may be used,\n and vocabulary-relative IRIs use string concatenation rather than\n IRI resolution, it is possible to construct IRIs that may be\n used maliciously, if dereferenced.","Interoperability considerations:","Not Applicable","Published specification:","http://www.w3.org/TR/json-ld","Applications that use this media type:","Any programming environment that requires the exchange of\n directed graphs. Implementations of JSON-LD have been created for\n JavaScript, Python, Ruby, PHP, and C++.\n ","Additional information:","Magic number(s):","File extension(s):",".jsonld","Macintosh file type code(s):","TEXT","Person & email address to contact for further information:","Ivan Herman ","Intended usage:","Common","Restrictions on usage:","Author(s):","Manu Sporny, Dave Longley, Gregg Kellogg, Markus Lanthaler, Niklas Lindström","Change controller:","Fragment identifiers used with application/ld+json\n are treated as in RDF syntaxes, as per\n RDF 1.1 Concepts and Abstract Syntax\n [RDF11-CONCEPTS].","This registration is an update to the original definition\n for application/ld+json\n in [JSON-LD10].","C.1 Examples","The following examples illustrate different ways in which the profile parameter may be used\n to describe different acceptable responses.","\n Example 166: HTTP Request with profile requesting an expanded document\n ","GET/ordinary-json-document.json HTTP/1.1\nHost: example.com\nAccept: application/ld+json;profile=http://www.w3.org/ns/json-ld#expanded","Requests the server to return the requested resource as JSON-LD\n in expanded document form.","\n Example 167: HTTP Request with profile requesting a compacted document\n ","GET/ordinary-json-document.json HTTP/1.1\nHost: example.com\nAccept: application/ld+json;profile=http://www.w3.org/ns/json-ld#compacted","Requests the server to return the requested resource as JSON-LD\n in compacted document form.\n As no explicit context resource is specified, the server compacts\n using an application-specific default context.","\n Example 168: HTTP Request with profile requesting a compacted document with a reference to a compaction context\n ","GET/ordinary-json-document.json HTTP/1.1\nHost: example.com\nAccept: application/ld+json;profile=\"http://www.w3.org/ns/json-ld#flattened http://www.w3.org/ns/json-ld#compacted\"","Requests the server to return the requested resource as JSON-LD\n in both ",".\n Note that as whitespace is used to separate the two URIs, they\n are enclosed in double quotes (","D. Open Issues","The following is a list of issues open at the time of publication.","Issue 108: Consider context by reference with metadata defer-future-versionprivacy-trackersecurity-tracker","Consider context by reference with metadata.","Issue 191: Compact IRI expansion support for non-trivial prefix term definitions defer-future-versionspec:enhancement","Compact IRI expansion support for non-trivial prefix term definitions.","Issue 280: language-maps don't allow separate base direction defer-future-version","Language-maps don't allow separate base direction.","Issue 328: @default in @context in JSON-LD core syntax defer-future-version"," in JSON-LD core syntax.","Issue 329: Suggestion about `@prefix` defer-future-version","Suggestion about ","Issue 335: Type Coercion / Node Conversion: @coerce keyword or similar defer-future-version","Type Coercion / Node Conversion: @coerce keyword or similar.","E. Changes since 1.0 Recommendation of 16 January 2014","A context may contain a "," which is used to set the "," can now have an\n "," property, which defines a "," used for values of\n a "," identified with such a "," values within an "," may now\n include ",", corresponding to "," property, which identifies a term expanding to\n "," which is used for containing properties using the same\n "," mapping. When expanding, the values of a property\n expanding to "," are treated as if they were contained\n within the enclosing "," directly.","The JSON syntax has been abstracted into an internal representation\n to allow for other serializations that are functionally equivalent\n to JSON.","Added § 4.6.3 Node Identifier Indexing and § 4.6.4 Node Type Indexing.","Both ","language maps"," may legitimately have an "," key, but\n "," only allowed "," keys. This has been updated\n to allow "," keys.","The value for ","\n can also be an "," containing any appropriate container\n keyword along with "," (other than ",").\n This allows a way to ensure that such property values will always\n be expressed in "," form.","In JSON-LD 1.1, terms will be chosen as "," prefixes\n when compacting only if\n a "," character,\n or if their "," contains\n a ",". The 1.0 algorithm has\n been updated to only consider terms that map to a value that ends with a URI\n "," character.","Values of properties where the associated ","\n has "," are interpreted as\n ","implicitly named graphs",", where the associated graph name is\n assigned from a new ",". Other combinations\n include ","[\"@container\", \"@id\"]","[\"@container\", \"@index\"]"," each also\n may include ","\"@set\"",", which create maps from the\n graph identifier or index value similar to ","Additionally, see § F. Changes since JSON-LD Community Group Final Report.","F. Changes since JSON-LD Community Group Final Report","Lists may now have items which are themselves lists.","Values of ",", or an alias of ",", may now have their ","\n to ensure that "," are always represented as an array. This\n also allows a term to be defined for ",", where the value ","\n with ","The use of blank node identifiers to label properties is obsolete,\n and may be removed in a future version of JSON-LD, as is the support for generalized RDF Datasets.","The vocabulary mapping can be a relative IRI reference, which is evaluated\n either against an existing default vocabulary, or against the document base.\n This allows vocabulary-relative IRIs, such as the\n keys of node objects, are expanded or compacted relative\n to the document base.\n (See Security Considerations in § C. IANA Considerations\n for a discussion on how string vocabulary-relative IRI resolution via concatenation.\n )","Added support for "," to prevent value compaction.\n Define the "," datatype.","Term definitions with keys which are of the form of an IRI reference or a compact IRIMUST NOT\n expand to an IRI other than the expansion of the key itself."," may also be located within an HTML document, identified\n using type ","Term definitions can now be protected,\n to limit the ability of other contexts to override them."," defined in an "," may also be used for values\n of ",", which defines a "," to use for "," including the associated type.","By default, all contexts are propagated when traversing ",", other than\n ",". This can be controlled using the ","A context may contain an "," used to reference a remote context\n within a context, allowing "," features to be added to contexts originally\n authored for ","A node object may include an included block,\n which is used to contain a set of node objects which are treated\n exactly as if they were node objects defined in an array including the containing\n node object.\n This allows the use of the object form of a JSON-LD document when there is more\n than one node object being defined, and where those node objects\n are not embedded as values of the containing node object."," link relation can be used to supply an alternate location for\n retrieving a JSON-LD document when the returned document is not JSON.",", and associated "," have been updated to \n support "," for setting the "," of strings."," is now implicitly ",", unless set\n explicitly to ","Improve notation using IRI, IRI reference, and relative IRI reference.","Warn about forward-compatibility issues for terms of the form (","\"@\"1*ALPHA","When creating an "," datatype or ","language tags"," are\n normalized to lower case to improve interoperability between implementations.","G. Changes since Candidate Release of 12 December 2019","Expand "," to describe the behavior\n of ","\"@prefix\": false"," for ",", and to note that this affects both expansion\n of "," and compaction of ","Adding a missing normative definition of the "," keyword used within\n an ","§ 9.15.1 Expanded term definition","Changed normative definition of the "," datatype in ","\n to describe a normative canonicalization.\n This is in response to ","Issue 323","Updated the non-normative definitions of the "," based datatype in "," class in ","\n to normalize language tags to lowercase when generating RDF.","H. Changes since Proposed Recommendation Release of 7 May 2020","Removed remaining \"at-risk\" notes.","Update bibliographic reference for JCS to [RFC8785].","Fixed typo in ","§ 9.3 Frame Objects",",\n which was unintentionally diverging from the normative description of the "," keyword in ",".\n This is in response to ","Issue 358","I. Acknowledgements","\n The editors would like to specially thank the following individuals for making significant\n contributions to the authoring and editing of this specification:\n ","Timothy Cole (University of Illinois at Urbana-Champaign)","Gregory Todd Williams (J. Paul Getty Trust)","Ivan Herman (W3C Staff)","Jeff Mixter (OCLC (Online Computer Library Center, Inc.))","David Lehn (Digital Bazaar)","David Newbury (J. Paul Getty Trust)","Robert Sanderson (J. Paul Getty Trust, chair)","Harold Solbrig (Johns Hopkins Institute for Clinical and Translational Research)","Simon Steyskal (WU (Wirschaftsuniversität Wien) - Vienna University of Economics and Business)","A Soroka (Apache Software Foundation)","Ruben Taelman (Imec vzw)","Benjamin Young (Wiley, chair)","Additionally, the following people were members of the Working Group at the time of publication:","Steve Blackmon (Apache Software Foundation)","Dan Brickley (Google, Inc.)","Newton Calegari (NIC.br - Brazilian Network Information Center)","Victor Charpenay (Siemens AG)","Sebastian Käbisch (Siemens AG)","Axel Polleres (WU (Wirschaftsuniversität Wien) - Vienna University of Economics and Business)","Leonard Rosenthol (Adobe)","Jean-Yves ROSSI (CANTON CONSULTING)","Antoine Roulin (CANTON CONSULTING)","Manu Sporny (Digital Bazaar)","Clément Warnier de Wailly (CANTON CONSULTING)","\n A large amount of thanks goes out to the JSON-LD Community Group participants who worked through many of the technical issues on the mailing list and the weekly telecons: Chris Webber, David Wood, Drummond Reed, Eleanor Joslin, Fabien Gandon, Herm Fisher, Jamie Pitts, Kim Hamilton Duffy, Niklas Lindström, Paolo Ciccarese, Paul Frazze, Paul Warren, Reto Gmür, Rob Trainer, Ted Thibodeau Jr., and Victor Charpenay.\n ","J. References","J.1 \n Normative references\n ","[BCP47]","Tags for Identifying Languages. A. Phillips; M. Davis. IETF. September 2009. IETF Best Current Practice. URL: https://tools.ietf.org/html/bcp47","[DOM]","DOM Standard. Anne van Kesteren. WHATWG. Living Standard. URL: https://dom.spec.whatwg.org/","[ECMASCRIPT]","ECMAScript Language Specification. Ecma International. URL: https://tc39.es/ecma262/","[HTML]","HTML Standard. Anne van Kesteren; Domenic Denicola; Ian Hickson; Philip Jägenstedt; Simon Pieters. WHATWG. Living Standard. URL: https://html.spec.whatwg.org/multipage/","[IANA-URI-SCHEMES]","Uniform Resource Identifier (URI) Schemes. IANA. URL: https://www.iana.org/assignments/uri-schemes/uri-schemes.xhtml","[JSON]","The application/json Media Type for JavaScript Object Notation (JSON). D. Crockford. IETF. July 2006. Informational. URL: https://tools.ietf.org/html/rfc4627","[JSON-LD10]","JSON-LD 1.0. Manu Sporny; Gregg Kellogg; Marcus Langhaler. W3C. 16 January 2014. W3C Recommendation. URL: https://www.w3.org/TR/2014/REC-json-ld-20140116/","[JSON-LD11-API]","JSON-LD 1.1 Processing Algorithms and API. Gregg Kellogg; Dave Longley; Pierre-Antoine Champin. W3C. 7 May 2020. W3C Proposed Recommendation. URL: https://www.w3.org/TR/json-ld11-api/","[JSON-LD11-FRAMING]","JSON-LD 1.1 Framing. Dave Longley; Gregg Kellogg; Pierre-Antoine Champin. W3C. 7 May 2020. W3C Proposed Recommendation. URL: https://www.w3.org/TR/json-ld11-framing/","[RDF-SCHEMA]","RDF Schema 1.1. Dan Brickley; Ramanathan Guha. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/rdf-schema/","[RDF11-CONCEPTS]","RDF 1.1 Concepts and Abstract Syntax. Richard Cyganiak; David Wood; Markus Lanthaler. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/rdf11-concepts/","[RDF11-MT]","RDF 1.1 Semantics. Patrick Hayes; Peter Patel-Schneider. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/rdf11-mt/","[RFC2119]","Key words for use in RFCs to Indicate Requirement Levels. S. Bradner. IETF. March 1997. Best Current Practice. URL: https://tools.ietf.org/html/rfc2119","[RFC3986]","Uniform Resource Identifier (URI): Generic Syntax. T. Berners-Lee; R. Fielding; L. Masinter. IETF. January 2005. Internet Standard. URL: https://tools.ietf.org/html/rfc3986","[RFC3987]","Internationalized Resource Identifiers (IRIs). M. Duerst; M. Suignard. IETF. January 2005. Proposed Standard. URL: https://tools.ietf.org/html/rfc3987","[RFC4288]","Media Type Specifications and Registration Procedures. N. Freed; J. Klensin. IETF. December 2005. Best Current Practice. URL: https://tools.ietf.org/html/rfc4288","[RFC5234]","Augmented BNF for Syntax Specifications: ABNF. D. Crocker, Ed.; P. Overell. IETF. January 2008. Internet Standard. URL: https://tools.ietf.org/html/rfc5234","[RFC6839]","Additional Media Type Structured Syntax Suffixes. T. Hansen; A. Melnikov. IETF. January 2013. Informational. URL: https://tools.ietf.org/html/rfc6839","[RFC6906]","The 'profile' Link Relation Type. E. Wilde. IETF. March 2013. Informational. URL: https://tools.ietf.org/html/rfc6906","[RFC7231]","Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content. R. Fielding, Ed.; J. Reschke, Ed. June 2014. Proposed Standard. URL: https://tools.ietf.org/html/rfc7231","[RFC8174]","Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words. B. Leiba. IETF. May 2017. Best Current Practice. URL: https://tools.ietf.org/html/rfc8174","[RFC8259]","The JavaScript Object Notation (JSON) Data Interchange Format. T. Bray, Ed.. IETF. December 2017. Internet Standard. URL: https://tools.ietf.org/html/rfc8259","[RFC8288]","Web Linking. M. Nottingham. October 2017. Proposed Standard. URL: https://tools.ietf.org/html/rfc8288","[UAX9]","Unicode Bidirectional Algorithm. Mark Davis; Aharon Lanin; Andrew Glass. Unicode Consortium. 12 February 2020. Unicode Standard Annex #9. URL: https://www.unicode.org/reports/tr9/tr9-42.html","[UNICODE]","The Unicode Standard. Unicode Consortium. URL: https://www.unicode.org/versions/latest/","J.2 \n Informative references\n ","[fingerprinting-guidance]","Mitigating Browser Fingerprinting in Web Specifications. Nick Doty. W3C. 28 March 2019. W3C Note. URL: https://www.w3.org/TR/fingerprinting-guidance/","[INFRA]","Infra Standard. Anne van Kesteren; Domenic Denicola. WHATWG. Living Standard. URL: https://infra.spec.whatwg.org/","[JSON.API]","JSON API. Steve Klabnik; Yehuda Katz; Dan Gebhardt; Tyler Kellen; Ethan Resnick. 29 May 2015. unofficial. URL: https://jsonapi.org/format/","[ld-glossary]","Linked Data Glossary. Bernadette Hyland; Ghislain Auguste Atemezing; Michael Pendleton; Biplav Srivastava. W3C. 27 June 2013. W3C Note. URL: https://www.w3.org/TR/ld-glossary/","[LINKED-DATA]","Linked Data Design Issues. Tim Berners-Lee. W3C. 27 July 2006. W3C-Internal Document. URL: https://www.w3.org/DesignIssues/LinkedData.html","[MICRODATA]","HTML Microdata. Charles 'chaals' (McCathie) Nevile; Dan Brickley; Ian Hickson. W3C. 26 April 2018. W3C Working Draft. URL: https://www.w3.org/TR/microdata/","[RDFA-CORE]","RDFa Core 1.1 - Third Edition. Ben Adida; Mark Birbeck; Shane McCarron; Ivan Herman et al. W3C. 17 March 2015. W3C Recommendation. URL: https://www.w3.org/TR/rdfa-core/","[rfc4122]","A Universally Unique IDentifier (UUID) URN Namespace. P. Leach; M. Mealling; R. Salz. IETF. July 2005. Proposed Standard. URL: https://tools.ietf.org/html/rfc4122","[RFC7049]","Concise Binary Object Representation (CBOR). C. Bormann; P. Hoffman. IETF. October 2013. Proposed Standard. URL: https://tools.ietf.org/html/rfc7049","[RFC7946]","The GeoJSON Format. H. Butler; M. Daly; A. Doyle; S. Gillies; S. Hagen; T. Schaub. IETF. August 2016. Proposed Standard. URL: https://tools.ietf.org/html/rfc7946","[RFC8785]","JSON Canonicalization Scheme (JCS). A. Rundgren; B. Jordan; S. Erdtman. Network Working Group. June 2020. Informational. URL: https://www.rfc-editor.org/rfc/rfc8785","[SPARQL11-OVERVIEW]","SPARQL 1.1 Overview. The W3C SPARQL Working Group. W3C. 21 March 2013. W3C Recommendation. URL: https://www.w3.org/TR/sparql11-overview/","[SRI]","Subresource Integrity. Devdatta Akhawe; Frederik Braun; Francois Marier; Joel Weinberger. W3C. 23 June 2016. W3C Recommendation. URL: https://www.w3.org/TR/SRI/","[string-meta]","Strings on the Web: Language and Direction Metadata. Addison Phillips; Richard Ishida. W3C. 11 June 2019. W3C Working Draft. URL: https://www.w3.org/TR/string-meta/","[TriG]","RDF 1.1 TriG. Gavin Carothers; Andy Seaborne. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/trig/","[Turtle]","RDF 1.1 Turtle. Eric Prud'hommeaux; Gavin Carothers. W3C. 25 February 2014. W3C Recommendation. URL: https://www.w3.org/TR/turtle/","[URN]","URN Syntax. R. Moats. IETF. May 1997. Proposed Standard. URL: https://tools.ietf.org/html/rfc2141","[WEBIDL]","Web IDL. Boris Zbarsky. W3C. 15 December 2016. W3C Editor's Draft. URL: https://heycam.github.io/webidl/","[YAML]","YAML Ain’t Markup Language (YAML™) Version 1.2. Oren Ben-Kiki; Clark Evans; Ingy döt Net. 1 October 2009. URL: http://yaml.org/spec/1.2/spec.html","↑"]}
JSON is a useful data serialization and messaging format.
This specification defines JSON-LD 1.1, a JSON-based format to serialize
Linked Data. The syntax is designed to easily integrate into deployed
systems that already use JSON, and provides a smooth upgrade path from
JSON to JSON-LD.
It is primarily intended to be a way to use Linked Data in Web-based
programming environments, to build interoperable Web services, and to
store Linked Data in JSON-based storage engines.
This specification describes a superset of the features defined in
JSON-LD 1.0 [JSON-LD10]
and, except where noted,
documents created using the 1.0 version of this specification remain compatible with JSON-LD 1.1.
Status of This Document
This section describes the status of this
document at the time of its publication. Other documents may supersede
this document. A list of current W3C publications and the latest revision
of this technical report can be found in the
W3C technical reports index at
https://www.w3.org/TR/.
GitHub Issues are preferred for
discussion of this specification.
Alternatively, you can send comments to our mailing list.
Please send them to
public-json-ld-wg@w3.org
(archives).
This document has been reviewed by W3C Members, by software developers, and
by other W3C groups and interested parties, and is endorsed by the Director
as a W3C Recommendation. It is a stable document and may be used as
reference material or cited from another document. W3C's role in making the
Recommendation is to draw attention to the specification and to promote its
widespread deployment. This enhances the functionality and interoperability
of the Web.
This document was produced by a group
operating under the
W3C Patent Policy.
W3C maintains a
public list of any patent disclosures
made in connection with the deliverables of
the group; that page also includes
instructions for disclosing a patent. An individual who has actual
knowledge of a patent which the individual believes contains
Essential Claim(s)
must disclose the information in accordance with
section 6 of the W3C Patent Policy.
Linked Data [LINKED-DATA] is a way to create a network of
standards-based machine interpretable data across different documents and
Web sites. It allows an application to start at one piece of Linked Data,
and follow embedded links to other pieces of Linked Data that are hosted on
different sites across the Web.
JSON-LD is a lightweight syntax to serialize Linked Data in
JSON [RFC8259]. Its design allows existing JSON to be interpreted as
Linked Data with minimal changes. JSON-LD is primarily intended to be a
way to use Linked Data in Web-based programming environments, to build
interoperable Web services, and to store Linked Data in JSON-based storage engines. Since
JSON-LD is 100% compatible with JSON, the large number of JSON parsers and libraries
available today can be reused. In addition to all the features JSON provides,
JSON-LD introduces:
a universal identifier mechanism for JSON objects
via the use of IRIs,
a way to disambiguate keys shared among different JSON documents by mapping
them to IRIs via a context,
a mechanism in which a value in a JSON object may refer
to a resource on a different site on the Web,
the ability to annotate strings with their language,
a way to associate datatypes with values such as dates and times,
and a facility to express one or more directed graphs, such as a social
network, in a single document.
JSON-LD is designed to be usable directly as JSON, with no knowledge of RDF
[RDF11-CONCEPTS]. It is also designed to be usable as RDF
in conjunction with other Linked Data technologies like SPARQL [SPARQL11-OVERVIEW].
Developers who
require any of the facilities listed above or need to serialize an RDF graph
or Dataset in a JSON-based syntax will find JSON-LD of interest. People
intending to use JSON-LD with RDF tools will find it can be used as another
RDF syntax, as with [Turtle] and [TriG]. Complete details of how JSON-LD relates
to RDF are in section § 10. Relationship to RDF.
The syntax is designed to not disturb already
deployed systems running on JSON, but provide a smooth upgrade path from
JSON to JSON-LD. Since the shape of such data varies wildly, JSON-LD
features mechanisms to reshape documents into a deterministic structure
which simplifies their processing.
1.1 How to Read this Document
This section is non-normative.
This document is a detailed specification for a serialization of Linked
Data in JSON. The document is primarily intended for the following audiences:
Software developers who want to encode Linked Data in a variety of
programming languages that can use JSON
Software developers who want to convert existing JSON to JSON-LD
Software developers who want to understand the design decisions and
language syntax for JSON-LD
Software developers who want to implement processors and APIs for
JSON-LD
Software developers who want to generate or consume Linked Data,
an RDF graph, or an RDF Dataset in a JSON syntax
A companion document, the JSON-LD 1.1 Processing Algorithms and API specification
[JSON-LD11-API], specifies how to work with JSON-LD at a higher level by
providing a standard library interface for common JSON-LD operations.
To understand the basics in this specification you must first be familiar with
JSON, which is detailed in [RFC8259].
This document almost exclusively uses the term IRI
(Internationalized Resource Indicator)
when discussing hyperlinks. Many Web developers are more familiar with the
URL (Uniform Resource Locator)
terminology. The document also uses, albeit rarely, the URI
(Uniform Resource Indicator)
terminology. While these terms are often used interchangeably among
technical communities, they do have important distinctions from one
another and the specification goes to great lengths to try and use the
proper terminology at all times.
This document can highlight changes since the JSON-LD 1.0 version.
Select to changes.
1.2 Contributing
This section is non-normative.
There are a number of ways that one may participate in the development of
this specification:
Technical discussion typically occurs on the working group mailing list:
public-json-ld-wg@w3.org
The working group uses #json-ld
IRC channel is available for real-time discussion on irc.w3.org.
The #json-ld
IRC channel is also available for real-time discussion on irc.freenode.net.
1.3 Typographical conventions
This section is non-normative.
The following typographic conventions are used in this specification:
markup
Markup (elements, attributes, properties),
machine processable values (string, characters, media types),
property name,
or a file name is in red-orange monospace font.
variable
A variable in pseudo-code or in an algorithm description is in italics.
definition
A definition of a term, to be used elsewhere in this or other specifications,
is in bold and italics.
A references to a definition in this document,
when the reference itself is also a markup, is underlined,
red-orange monospace font, and is also an active link to the definition itself.
A reference to a definition in another document,
when the reference itself is also a markup,
is underlined, in italics red-orange monospace font,
and is also an active link to the definition itself.
Examples are in light khaki boxes, with khaki left border,
and with a numbered "Example" header in khaki.
Examples are always informative. The content of the example is in monospace font and may be syntax colored.
Examples may have tabbed navigation buttons
to show the results of transforming an example into other representations.
1.4 Terminology
This section is non-normative.
This document uses the following terms as defined in external specifications
and defines terms specific to JSON-LD.
In the JSON serialization,
an array structure is represented as square brackets surrounding zero or more values.
Values are separated by commas.
In the internal representation,
a list (also called an array) is an ordered collection of zero or more values.
While JSON-LD uses the same array representation as JSON,
the collection is unordered by default.
While order is preserved in regular JSON arrays,
it is not in regular JSON-LD arrays unless specifically defined
(see the Sets and Lists section of JSON-LD 1.1.
In the JSON serialization,
an object structure
is represented as a pair of curly brackets surrounding zero or more name/value pairs (or members).
A name is a string.
A single colon comes after each name,
separating the name from the value.
A single comma separates a value from a following name.
In JSON-LD the names in an object must be unique.
The use of the null value within JSON-LD
is used to ignore or reset values.
A map entry in the @context where the value,
or the @id of the value, is null,
explicitly decouples a term's association with an IRI.
A map entry in the body of a JSON-LD document
whose value is null
has the same meaning as if the map entry was not defined.
If @value, @list, or @set is set to null in expanded form,
then the entire JSON object is ignored.
In the JSON serialization, a number
is similar to that used in most programming languages,
except that the octal and hexadecimal formats are not used and that leading zeros are not allowed.
In the internal representation,
a number is equivalent to either a long
or double,
depending on if the number has a non-zero fractional part (see [WEBIDL]).
A string
is a sequence of zero or more Unicode (UTF-8) characters,
wrapped in double quotes, using backslash escapes (if necessary).
A character is represented as a single character string.
A relative IRI reference is an IRI reference that is relative to some other IRI,
typically the base IRI of the document.
Note that properties,
values of @type,
and values of terms defined to be vocabulary relative
are resolved relative to the vocabulary mapping,
not the base IRI.
A node in a graph that is neither an IRI,
nor a literal.
A blank node does not contain
a de-referenceable identifier because it is either ephemeral in nature
or does not contain information that needs to be linked to from outside of the linked data graph.
In JSON-LD,
a blank node is assigned an identifier starting with the prefix _:.
A blank node identifier
is a string that can be used as an identifier for a blank node within the scope of a JSON-LD document.
Blank node identifiers begin with _:.
An object expressed as a value such as a string or number.
Implicitly or explicitly includes a datatype IRI and, if the datatype is rdf:langString, an optional language tag.
A context that is used to resolve terms
while the processing algorithm is running.
base direction
The base direction is the direction used when a string does not have a direction associated with it directly.
It can be set in the context using the @direction key
whose value must be one of the strings "ltr", "rtl", or null.
See the Context Definitions section of JSON-LD 1.1 for a normative description.
compact IRI
A compact IRI has the form of prefix:suffix
and is used as a way of expressing an IRI without needing to define separate term definitions
for each IRI contained within a common vocabulary identified by prefix.
The default language is the language used when a string does not have a language associated with it directly.
It can be set in the context using the @language key
whose value must be a string representing a [BCP47] language code or null.
See the Context Definitions section of JSON-LD 1.1 for a normative description.
An expanded term definition is a term definition
where the value is a map
containing one or more keyword keys to define the associated IRI,
if this is a reverse property,
the type associated with string values, and a container mapping.
See the Expanded Term Definition section of JSON-LD 1.1 for a normative description.
A JSON-LD document,
which describes the form for transforming another JSON-LD document
using matching and embedding rules.
A frame document allows additional keywords and certain map entries
to describe the matching and transforming process.
A frame object is a map element within a frame
which represents a specific portion of the frame matching either
a node object or a value object
in the input.
See the Frame Objects section of JSON-LD 1.1 for a normative description.
An id map is a map value of a term
defined with @container set to @id.
The values of the id map must be node objects,
and its keys are interpreted as IRIs representing
the @id of the associated node object.
If a value in the id map contains a key expanding to @id,
its value must be equivalent to the referencing key in the id map.
See the Id Maps section of JSON-LD 1.1 for a normative description.
A JSON literal is a literal where the associated datatype IRI is rdf:JSON.
In the value object representation, the value of @type is @json.
JSON literals represent values which are valid JSON [RFC8259].
See the The rdf:JSON Datatype section in JSON-LD 1.1 for a normative description.
The JSON-LD internal representation
is the result of transforming a JSON syntactic structure
into the core data structures suitable for direct processing:
arrays, maps, strings, numbers, booleans, and null.
A JSON-LD Processor is a system which can perform the algorithms defined in JSON-LD 1.1 Processing Algorithms and API.
See the Conformance section in JSON-LD 1.1 API for a formal description.
A string that is specific to JSON-LD,
described in the Syntax Tokens and Keywords section of JSON-LD 1.1,
and normatively specified in the Keywords section of JSON-LD 1.1,
language map
An language map is a map value of a term
defined with @container set to @language,
whose keys must be strings representing [BCP47] language codes
and the values must be any of the following types:
null,
string, or
an array of zero or more of the above possibilities.
See the Language Maps section of JSON-LD 1.1 for a normative description.
list object
A list object is a map that has a @list key.
It may also have an @index key, but no other entries.
See the Lists and Sets section of JSON-LD 1.1 for a normative description.
local context
A context that is specified with a map,
specified via the @contextkeyword.
A node object used to reference a node having only the @id key.
prefix
A prefix is the first component of a compact IRI
which comes from a term that maps to a string that,
when prepended to the suffix of the compact IRI,
results in an IRI.
processing mode
The processing mode defines how a JSON-LD document is processed.
By default, all documents are assumed to be conformant with this specification.
By defining a different version using the @versionentry in a context,
publishers can ensure that processors conformant with JSON-LD 1.0 [JSON-LD10]
will not accidentally process JSON-LD 1.1 documents, possibly creating a different output.
The API provides an option for setting the processing mode to json-ld-1.0,
which will prevent JSON-LD 1.1 features from being activated,
or error if @versionentry in a context is explicitly set to 1.1.
This specification extends JSON-LD 1.0
via the json-ld-1.1processing mode.
scoped context
A scoped context is part of an expanded term definition using the
@contextentry. It has the same form as an embedded context.
When the term is used as a type, it defines a type-scoped context,
when used as a property it defines a property-scoped context.
set object
A set object is a map that has an @setentry.
It may also have an @index key, but no other entries.
See the Lists and Sets section of JSON-LD 1.1 for a normative description.
term
A term is a short word defined in a context
that may be expanded to an IRI.
See the Terms section of JSON-LD 1.1 for a normative description.
term definition
A term definition is an entry in a context,
where the key defines a term
which may be used within a map
as a key, type, or elsewhere that a string is interpreted as a vocabulary item.
Its value is either a string (simple term definition),
expanding to an IRI,
or a map (expanded term definition).
type map
A type map is a map value of a term
defined with @container set to @type,
whose keys are interpreted as IRIs
representing the @type of the associated node object;
the value must be a node object, or array of node objects.
If the value contains a term expanding to @type,
its values are merged with the map value when expanding.
See the Type Maps section of JSON-LD 1.1 for a normative description.
typed value
A typed value consists of a value,
which is a string,
and a type,
which is an IRI.
The vocabulary mapping is set in the context using the @vocab key
whose value must be an IRI, a compact IRI, a term, or null.
See the Context Definitions section of JSON-LD 1.1 for a normative description.
1.5 Design Goals and Rationale
This section is non-normative.
JSON-LD satisfies the following design goals:
Simplicity
No extra processors or software libraries are necessary to use JSON-LD
in its most basic form. The language provides developers with a very easy
learning curve. Developers not concerned with Linked Data only need to understand JSON,
and know to include but ignore the @context property,
to use the basic functionality in JSON-LD.
Compatibility
A JSON-LD document is always a valid JSON document. This ensures that
all of the standard JSON libraries work seamlessly with JSON-LD documents.
Expressiveness
The syntax serializes labeled directed graphs. This ensures that almost
every real world data model can be expressed.
Terseness
The JSON-LD syntax is very terse and human readable, requiring as
little effort as possible from the developer.
Zero Edits, most of the time
JSON-LD ensures a smooth and simple transition from existing
JSON-based systems. In many cases,
zero edits to the JSON document and the addition of one line to the HTTP response
should suffice (see § 6.1 Interpreting JSON as JSON-LD).
This allows organizations that have
already deployed large JSON-based infrastructure to use JSON-LD's features
in a way that is not disruptive to their day-to-day operations and is
transparent to their current customers. However, there are times where
mapping JSON to a graph representation is a complex undertaking.
In these instances, rather than extending JSON-LD to support
esoteric use cases, we chose not to support the use case. While Zero
Edits is a design goal, it is not always possible without adding
great complexity to the language. JSON-LD focuses on simplicity when
possible.
Usable as RDF
JSON-LD is usable by developers as
idiomatic JSON, with no need to understand RDF [RDF11-CONCEPTS].
JSON-LD is also usable as RDF, so people intending to use JSON-LD
with RDF tools will find it can be used like any other RDF syntax.
Complete details of how JSON-LD relates to RDF are in section
§ 10. Relationship to RDF.
1.6 Data Model Overview
This section is non-normative.
Generally speaking, the data model described by a JSON-LD document is a labeled, directed graph.
The graph contains nodes, which are connected by directed-arcs.
A node is either a resource with properties, or the data values of those properties including
strings, numbers, typed values (like dates and times) and IRIs.
Within a directed graph, nodes are resources, and may
be unnamed, i.e., not identified by an IRI;
which are called blank nodes,
and may be identified using a blank node identifier.
These identifiers may be required to represent a fully connected graph
using a tree structure, such as JSON, but otherwise have no
intrinsic meaning.
Literal values, such as strings and numbers, are also considered resources,
and JSON-LD distinguishes between node objects and value objects to distinguish between the different
kinds of resource.
This simple data model is incredibly
flexible and powerful, capable of modeling almost any kind of
data. For a deeper explanation of the data model, see
section § 8. Data Model.
Developers who are familiar with Linked Data technologies will
recognize the data model as the RDF Data Model. To dive deeper into how
JSON-LD and RDF are related, see
section § 10. Relationship to RDF.
At the surface level, a JSON-LD document is simply
JSON, detailed in [RFC8259].
For the purpose of describing the core data structures,
this is limited to arrays, maps (the parsed version of a JSON Object),
strings, numbers, booleans, and null,
called the JSON-LD internal representation.
This allows surface syntaxes other than JSON
to be manipulated using the same algorithms, when the syntax maps
to equivalent core data structures.
JSON-LD specifies a number of syntax tokens and keywords
that are a core part of the language.
A normative description of the keywords is given in § 9.16 Keywords.
:
The separator for JSON keys and values that use compact IRIs.
Used to define the short-hand names that are used throughout a JSON-LD
document. These short-hand names are called terms and help
developers to express specific identifiers in a compact manner. The
@context keyword is described in detail in
§ 3.1 The Context.
Used in a context definition to load an external context
within which the containing context definition is merged.
This can be useful to add JSON-LD 1.1 features to JSON-LD 1.0 contexts.
Used to specify that a container is used to index information and
that processing should continue deeper into a JSON data structure.
This keyword is described in § 4.6.1 Data Indexing.
Used to specify the language for a particular string value or the default
language of a JSON-LD document. This keyword is described in
§ 4.2.4 String Internationalization.
@list
Used to express an ordered set of data.
This keyword is described in § 4.3.1 Lists.
@nest
Used to define a property of a node object that groups together properties of that node, but is not an edge in the graph.
@none
Used as an index value
in an index map, id map, language map, type map, or elsewhere where a map is
used to index into other values, when the indexed node does not have the feature being indexed.
@prefix
With the value true, allows this term to be used to construct a compact IRI
when compacting.
With the value false prevents the term from being used to construct a compact IRI.
Also determines if the term will be considered when expanding compact IRIs.
@propagate
Used in a context definition to change the scope of that context.
By default, it is true,
meaning that contexts propagate across node objects
(other than for type-scoped contexts, which default to false).
Setting this to false causes term definitions created within that context
to be removed when entering a new node object.
The use of @type to define a type for both
node objects and value objects addresses the basic need to type data,
be it a literal value or a more complicated resource.
Experts may find the overloaded use of the @type keyword for both purposes concerning,
but should note that Web developer usage of this feature over multiple years
has not resulted in its misuse due to the far less frequent use of @type
to express typed literal values.
Within a context definition@version takes the specific value 1.1, not
"json-ld-1.1", as a JSON-LD 1.0 processor may accept a string value for @version,
but will reject a numeric value.
Note
The use of 1.1 for the value of @version is intended to
cause a JSON-LD 1.0 processor to stop processing.
Although it is clearly meant to be related to JSON-LD 1.1, it does not
otherwise adhere to the requirements for Semantic Versioning.
@vocab
Used to expand properties and values in @type with a common prefix
IRI. This keyword is described in § 4.1.2 Default Vocabulary.
All keys, keywords, and values in JSON-LD are case-sensitive.
2. Conformance
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The key words MAY, MUST, MUST NOT, RECOMMENDED, SHOULD, and SHOULD NOT in this document
are to be interpreted as described in
BCP 14
[RFC2119] [RFC8174]
when, and only when, they appear in all capitals, as shown here.
A JSON-LD document complies with this specification if it follows
the normative statements in appendix § 9. JSON-LD Grammar. JSON documents
can be interpreted as JSON-LD by following the normative statements in
§ 6.1 Interpreting JSON as JSON-LD. For convenience, normative
statements for documents are often phrased as statements on the properties of the document.
This specification makes use of the following namespace prefixes:
Prefix
IRI
dc11
http://purl.org/dc/elements/1.1/
dcterms
http://purl.org/dc/terms/
cred
https://w3id.org/credentials#
foaf
http://xmlns.com/foaf/0.1/
geojson
https://purl.org/geojson/vocab#
prov
http://www.w3.org/ns/prov#
i18n
https://www.w3.org/ns/i18n#
rdf
http://www.w3.org/1999/02/22-rdf-syntax-ns#
schema
http://schema.org/
skos
http://www.w3.org/2004/02/skos/core#
xsd
http://www.w3.org/2001/XMLSchema#
These are used within this document as part of a compact IRI
as a shorthand for the resulting IRI, such as dcterms:title
used to represent http://purl.org/dc/terms/title.
3. Basic Concepts
This section is non-normative.
JSON [RFC8259] is a lightweight, language-independent data interchange format.
It is easy to parse and easy to generate. However, it is difficult to integrate JSON
from different sources as the data may contain keys that conflict with other
data sources. Furthermore, JSON has no
built-in support for hyperlinks, which are a fundamental building block on
the Web. Let's start by looking at an example that we will be using for the
rest of this section:
It's obvious to humans that the data is about a person whose
name is "Manu Sporny"
and that the homepage property contains the URL of that person's homepage.
A machine doesn't have such an intuitive understanding and sometimes,
even for humans, it is difficult to resolve ambiguities in such representations. This problem
can be solved by using unambiguous identifiers to denote the different concepts instead of
tokens such as "name", "homepage", etc.
Linked Data, and the Web in general, uses IRIs
(Internationalized Resource Identifiers as described in [RFC3987]) for unambiguous
identification. The idea is to use IRIs
to assign unambiguous identifiers to data that may be of use to other developers.
It is useful for terms,
like name and homepage, to expand to IRIs
so that developers don't accidentally step on each other's terms. Furthermore, developers and
machines are able to use this IRI (by using a web browser, for instance) to go to
the term and get a definition of what the term means. This process is known as IRI
dereferencing.
Leveraging the popular schema.org vocabulary,
the example above could be unambiguously expressed as follows:
In the example above, every property is unambiguously identified by an IRI and all values
representing IRIs are explicitly marked as such by the
@idkeyword. While this is a valid JSON-LD
document that is very specific about its data, the document is also overly verbose and difficult
to work with for human developers. To address this issue, JSON-LD introduces the notion
of a context as described in the next section.
When two people communicate with one another, the conversation takes
place in a shared environment, typically called
"the context of the conversation". This shared context allows the
individuals to use shortcut terms, like the first name of a mutual friend,
to communicate more quickly but without losing accuracy. A context in
JSON-LD works in the same way. It allows two applications to use shortcut
terms to communicate with one another more efficiently, but without
losing accuracy.
Simply speaking, a context is used to map terms to IRIs.
Terms are case sensitive and most valid strings that are not reserved JSON-LD keywords
can be used as a term.
Exceptions are the empty string "" and strings that have the form
of a keyword (i.e., starting with "@" followed exclusively by one or more ALPHA characters (see [RFC5234])), which must not be used as terms.
Strings that have the form of
an IRI (e.g., containing a ":") should not be used as terms.
For the sample document in the previous section, a context would
look something like this:
Example 4: Context for the sample document in the previous section
{
"@context": {
"name": "http://schema.org/name",↑ This means that 'name' is shorthand for 'http://schema.org/name'"image": {
"@id": "http://schema.org/image",↑ This means that 'image' is shorthand for 'http://schema.org/image'"@type": "@id"↑ This means that a string value associated with 'image'
should be interpreted as an identifier that is an IRI},
"homepage": {
"@id": "http://schema.org/url",↑ This means that 'homepage' is shorthand for 'http://schema.org/url'"@type": "@id"↑ This means that a string value associated with 'homepage'
should be interpreted as an identifier that is an IRI
}
}
}
Contexts can either be directly embedded
into the document (an embedded context) or be referenced using a URL.
Assuming the context document in the previous
example can be retrieved at https://json-ld.org/contexts/person.jsonld,
it can be referenced by adding a single line and allows a JSON-LD document to
be expressed much more concisely as shown in the example below:
The referenced context not only specifies how the terms map to
IRIs in the Schema.org vocabulary but also
specifies that string values associated with
the homepage and image property
can be interpreted as an IRI ("@type": "@id",
see § 3.2 IRIs for more details). This information allows developers
to re-use each other's data without having to agree to how their data will interoperate
on a site-by-site basis. External JSON-LD context documents may contain extra
information located outside of the @context key, such as
documentation about the terms declared in the
document. Information contained outside of the @context value
is ignored when the document is used as an external JSON-LD context document.
A remote context may also be referenced using a relative URL,
which is resolved relative to the location of the document containing the reference.
For example, if a document were located at http://example.org/document.jsonld
and contained a relative reference to context.jsonld,
the referenced context document would be found relative at http://example.org/context.jsonld.
Resolution of relative references to context URLs also applies to remote
context documents, as they may themselves contain references to other contexts.
In JSON-LD documents,
contexts may also be specified inline.
This has the advantage that documents can be processed even in the
absence of a connection to the Web. Ultimately, this is a modeling decision
and different use cases may require different handling.
See Security Considerations in § C. IANA Considerations
for a discussion on using remote contexts.
This section only covers the most basic features of the JSON-LD Context.
The Context can also be used to help interpret other more
complex JSON data structures, such as indexed values,
ordered values, and
nested properties.
More advanced features related to the JSON-LD Context are covered in
§ 4. Advanced Concepts.
As noted in § 1.1 How to Read this Document,
IRIs can often be confused with URLs (Uniform Resource Locators),
the primary distinction is that a URL locates a resource on the web,
an IRI identifies a resource. While it is a good practice for resource identifiers
to be dereferenceable, sometimes this is not practical. In particular, note the
[URN] scheme for Uniform Resource Names, such as UUID.
An example UUID is urn:uuid:f81d4fae-7dec-11d0-a765-00a0c91e6bf6.
In the example above, the key http://schema.org/name
is interpreted as an IRI.
Term-to-IRI expansion occurs if the key matches a term defined
within the active context:
JSON keys that do not expand to an IRI, such as status
in the example above, are not Linked Data and thus ignored when processed.
If type coercion rules are specified in the @context for
a particular term or property IRI, an IRI is generated:
In the example above, since the value http://manu.sporny.org/
is expressed as a JSON string, the type coercion
rules will transform the value into an IRI when processing the data.
See § 4.2.3 Type Coercion for more
details about this feature.
In summary, IRIs can be expressed in a variety of
different ways in JSON-LD:
An IRI is generated for the string value specified using
@id or @type.
An IRI is generated for the string value of any key for which there
are coercion rules that contain an @type key that is
set to a value of @id or @vocab.
This section only covers the most basic features associated with IRIs
in JSON-LD. More advanced features related to IRIs are covered in
section § 4. Advanced Concepts.
3.3 Node Identifiers
This section is non-normative.
To be able to externally reference nodes
in an RDF graph, it is important that
nodes have an identifier. IRIs
are a fundamental concept of Linked Data, for
nodes to be truly linked, dereferencing the
identifier should result in a representation of that node.
This may allow an application to retrieve further information about a
node.
In JSON-LD, a node is identified using the @idkeyword:
The example above contains a node object identified by the IRI
http://me.markus-lanthaler.com/.
This section only covers the most basic features associated with
node identifiers in JSON-LD. More advanced features related to
node identifiers are covered in section § 4. Advanced Concepts.
3.4 Uses of JSON Objects
This section is non-normative.
As a syntax, JSON has only a limited number of syntactic elements:
The JSON-LD data model allows for a richer set of resources, based on the RDF data model.
The data model is described more fully in § 8. Data Model.
JSON-LD uses JSON objects to describe various resources, along with the relationships
between these resources:
Node objects are used to define nodes in the linked data graph
which may have both incoming and outgoing edges.
Node objects are principle structure for defining resources having properties.
See § 9.2 Node Objects for the normative definition.
In Linked Data, it is common to specify the type of a graph node;
in many cases, this can be inferred based on the properties used within a
given node object, or the property for which a node is a value. For
example, in the schema.org vocabulary, the givenName
property is associated with a Person. Therefore, one may reason that
if a node object contains the property givenName, that the
type is a Person; making this explicit with @type helps
to clarify the association.
The type of a particular node can be specified using the @typekeyword. In Linked Data, types are uniquely
identified with an IRI.
A node can be assigned more than one type by using an array:
The value of a @type key may also be a term defined in the active context:
In addition to setting the type of nodes,
@type can also be used to set the type of a value
to create a typed value.
This use of @type is similar to that used to define the type of a node object,
but value objects are restricted to having just a single type.
The use of @type to create typed values is discussed more fully in § 4.2.1 Typed Values.
Typed values can also be defined implicitly, by specifying
@type in an expanded term definition.
This is covered more fully in § 4.2.3 Type Coercion.
4. Advanced Concepts
This section is non-normative.
JSON-LD has a number of features that provide functionality above and beyond
the core functionality described above. JSON can be used to express data
using such structures, and the features described in this
section can be used to interpret a variety of different JSON structures as
Linked Data. A JSON-LD processor will make use of provided and embedded
contexts to interpret property values in a number of different idiomatic
ways.
Describing values
One pattern in JSON is for the value of a property to be a string.
Often times, this string actually represents some other typed value, for
example an IRI, a date, or a string in some specific language. See § 4.2 Describing Values for details on how to
describe such value typing.
Value ordering
In JSON, a property with an array value implies an implicit order;
arrays in JSON-LD do not convey any ordering of the contained elements by
default, unless defined using embedded structures or through a context
definition. See § 4.3 Value Ordering for a
further discussion.
Property nesting
Another JSON idiom often found in APIs is to use an
intermediate object to group together related properties of an object; in JSON-LD
these are referred to as nested properties and are described in § 4.4 Nested Properties.
Referencing objects
Linked Data is all about describing the relationships between different resources.
Sometimes these relationships are between resources defined in different
documents described on the web, sometimes the resources are described
within the same document.
In this case, a document residing at http://manu.sporny.org/about
may contain the example above, and reference another document at
https://greggkellogg.net/foaf which could include a similar
representation.
A common idiom found in JSON usage is objects being specified as the
value of other objects, called object embedding in JSON-LD;
for example, a friend specified as an
object value of a Person:
Another common idiom in JSON is to use an intermediate object to represent property values via indexing. JSON-LD allows data to be indexed
in a number of different ways, as detailed in § 4.6 Indexed Values.
Reverse Properties
JSON-LD serializes directed graphs. That means that
every property points from a node to another node
or value. However, in some cases, it is desirable
to serialize in the reverse direction, as detailed in § 4.8 Reverse Properties.
The following sections describe such
advanced functionality in more detail.
4.1 Advanced Context Usage
This section is non-normative.
Section § 3.1 The Context introduced the basics of what makes
JSON-LD work. This section expands on the basic principles of the
context and demonstrates how more advanced use cases can
be achieved using JSON-LD.
In general, contexts may be used any time a
map is defined.
The only time that one cannot express a context is as a direct child of another context definition (other than as part of an expanded term definition).
For example, a JSON-LD document may
have the form of an array composed of one or more node objects,
which use a context definition in each top-level node object:
The outer array is standard for a document in
expanded document form
and flattened document form,
and may be necessary when describing a disconnected graph,
where nodes may not reference each other. In such cases, using
a top-level map with a @graph property can be useful for saving
the repetition of @context. See § 4.5 Embedding
for more.
Duplicate context terms are overridden using a
most-recently-defined-wins mechanism.
In the example above, the nameterm is overridden
in the more deeply nested details structure,
which uses its own embedded context.
Note that this is
rarely a good authoring practice and is typically used when working with
legacy applications that depend on a specific structure of the
map. If a term is redefined within a
context, all previous rules associated with the previous definition are
removed. If a term is redefined to null,
the term is effectively removed from the list of
terms defined in the active context.
Multiple contexts may be combined using an array, which is processed
in order. The set of contexts defined within a specific map are
referred to as local contexts. The
active context refers to the accumulation of
local contexts that are in scope at a
specific point within the document. Setting a local context
to null effectively resets the active context
to an empty context, without term definitions, default language,
or other things defined within previous contexts.
The following example specifies an external context
and then layers an embedded context on top of the external context:
When possible, the context definition should be put
at the top of a JSON-LD document. This makes the document easier to read and
might make streaming parsers more efficient. Documents that do not have the
context at the top are still conformant JSON-LD.
Note
To avoid forward-compatibility issues, terms
starting with an @ character
followed exclusively by one or more ALPHA characters (see [RFC5234])
are to be avoided as they
might be used as keyword in future versions
of JSON-LD. Terms starting with an @ character that are not
JSON-LD 1.1 keywords are treated as any other term, i.e.,
they are ignored unless mapped to an IRI. Furthermore, the use of
empty terms ("") is not allowed as
not all programming languages are able to handle empty JSON keys.
4.1.1 JSON-LD 1.1 Processing Mode
This section is non-normative.
New features defined in JSON-LD 1.1 are available
unless the processing mode is set to json-ld-1.0.
This may be set through an API option.
The processing mode may be explicitly set to json-ld-1.1 using the @versionentry in a context
set to the value 1.1 as a number, or through an API option.
Explicitly setting the processing mode to json-ld-1.1
will prohibit JSON-LD 1.0 processors from incorrectly processing a JSON-LD 1.1 document.
The first context encountered when processing a
document which contains @version determines the processing mode,
unless it is defined explicitly through an API option.
This means that if "@version": 1.1 is encountered after processing a context
without @version,
the former will be interpreted as having had "@version": 1.1 defined within it.
Note
Setting the processing mode explicitly
to json-ld-1.1 is RECOMMENDED to prevent a JSON-LD 1.0 processor
from incorrectly processing a JSON-LD 1.1 document and
producing different results.
4.1.2 Default Vocabulary
This section is non-normative.
At times, all properties and types may come from the same vocabulary. JSON-LD's
@vocab keyword allows an author to set a common prefix which
is used as the vocabulary mapping and is used
for all properties and types that do not match a term and are neither
an IRI nor a compact IRI (i.e., they do
not contain a colon).
If @vocab is used but certain keys in an
map should not be expanded using
the vocabulary IRI, a term can be explicitly set
to null in the context. For instance, in the
example below the databaseIdentry would not expand to an
IRI causing the property to be dropped when expanding.
The following example illustrates the affect of expanding a property using
a relative IRI reference, which is shown in the Expanded (Result) tab below.
Note
The grammar for @vocab, as defined in § 9.15 Context Definitions
allows the value to be a term or compact IRI.
Note that terms used in the value of @vocab must be in scope at the time the context is introduced,
otherwise there would be a circular dependency between @vocab and other terms defined in the same context.
This document uses an empty @id, which resolves to the document base.
However, if the document is moved to a different location, the IRI would change.
To prevent this without having to use an IRI, a context
may define an @base mapping, to overwrite the base IRI for the document.
Please note that the @base will be ignored if used in
external contexts.
4.1.4 Using the Document Base for the Default Vocabulary
This section is non-normative.
In some cases, vocabulary terms are defined directly within the document
itself, rather than in an external vocabulary.
Since JSON-LD 1.1, the vocabulary mapping in a local context
can be set to a relative IRI reference,
which is, if there is no vocabulary mapping in scope, resolved against the base IRI.
This causes terms which are expanded relative to the vocabulary,
such as the keys of node objects,
to be based on the base IRI to create IRIs.
If this document were located at http://example/document, it would expand as follows:
4.1.5 Compact IRIs
This section is non-normative.
A compact IRI is a way of expressing an IRI
using a prefix and suffix separated by a colon (:).
The prefix is a term taken from the
active context and is a short string identifying a
particular IRI in a JSON-LD document. For example, the
prefix foaf may be used as a shorthand for the
Friend-of-a-Friend vocabulary, which is identified using the IRIhttp://xmlns.com/foaf/0.1/. A developer may append
any of the FOAF vocabulary terms to the end of the prefix to specify a short-hand
version of the IRI for the vocabulary term. For example,
foaf:name would be expanded to the IRI
http://xmlns.com/foaf/0.1/name.
In the example above, foaf:name expands to the IRIhttp://xmlns.com/foaf/0.1/name and foaf:Person expands
to http://xmlns.com/foaf/0.1/Person.
Prefixes are expanded when the form of the value
is a compact IRI represented as a prefix:suffix
combination, the prefix matches a term defined within the
active context, and the suffix does not begin with two
slashes (//). The compact IRI is expanded by
concatenating the IRI mapped to the prefix to the (possibly empty)
suffix. If the prefix is not defined in the active context,
or the suffix begins with two slashes (such as in http://example.com),
the value is interpreted as IRI instead. If the prefix is an
underscore (_), the value is interpreted as blank node identifier
instead.
It's also possible to use compact IRIs within the context as shown in the
following example:
The term selection behavior for 1.0 processors was changed
as a result of an errata against JSON-LD 1.0 reported here.
This does not affect the behavior of processing existing JSON-LD documents, but creates
a slight change when compacting documents using Compact IRIs.
The behavior when compacting can be illustrated by considering the following input
document in expanded form:
Example 33: Expanded document used to illustrate compact IRI creation
Using the following context in the 1.0 processing mode
will now select the term vocab rather than
property, even though the IRI associated with
property captures more of the original IRI.
Compacting using the previous context with the above expanded input document
results in the following compacted result:
In the original [JSON-LD10],
the term selection algorithm would have selected property,
creating the Compact IRI property:One.
The original behavior can be made explicit using @prefix:
In this case, the property term would not normally be usable as a prefix, both
because it is defined with an expanded term definition, and because
its @id does not end in a
gen-delim character. Adding
"@prefix": true allows it to be used as the prefix portion of
the compact IRIproperty:One.
4.1.6 Aliasing Keywords
This section is non-normative.
Each of the JSON-LD keywords,
except for @context, may be aliased to application-specific
keywords. This feature allows legacy JSON content to be utilized
by JSON-LD by re-using JSON keys that already exist in legacy documents.
This feature also allows developers to design domain-specific implementations
using only the JSON-LD context.
In the example above, the @id and @typekeywords have been given the aliases
url and a, respectively.
Since keywords cannot be redefined, they can also not be aliased to
other keywords.
Note
Aliased keywords may not be used within a context, itself.
See § 9.16 Keywords for a normative
definition of all keywords.
4.1.7 IRI Expansion within a Context
This section is non-normative.
In general, normal IRI expansion rules apply
anywhere an IRI is expected (see § 3.2 IRIs). Within
a context definition, this can mean that terms defined
within the context may also be used within that context as long as
there are no circular dependencies. For example, it is common to use
the xsd namespace when defining typed values:
In this example, the compact IRI form is used in two different ways.
In the first approach, foaf:age declares both the
IRI for the term (using short-form) as well as the
@type associated with the term. In the second
approach, only the @type associated with the term is
specified. The full IRI for
foaf:homepage is determined by looking up the foafprefix in the
context.
Warning
If a compact IRI is used as a term, it must expand to the
value that compact IRI would have on its own when expanded.
This represents a change to the original 1.0 algorithm to prevent terms from
expanding to a different IRI, which could lead to undesired results.
Example 42: Illegal Aliasing of a compact IRI to a different IRI
In order for the IRI to match above, the IRI
needs to be used in the JSON-LD document. Also note that foaf:homepage
will not use the { "@type": "@id" } declaration because
foaf:homepage is not the same as http://xmlns.com/foaf/0.1/homepage.
That is, terms are looked up in a context using
direct string comparison before the prefix lookup mechanism is applied.
Warning
Neither an IRI reference nor a compact IRI
may expand to some other unrelated IRI.
This represents a change to the original 1.0 algorithm which allowed this behavior but discouraged it.
The only other exception for using terms in the context is that
circular definitions are not allowed. That is,
a definition of term1 cannot depend on the
definition of term2 if term2 also depends on
term1. For example, the following context definition
is illegal:
Example 44: Illegal circular definition of terms within a context
In this case, the social profile is defined using the schema.org vocabulary,
but interest is imported from FOAF,
and is used to define a node describing one of Manu's interests
where those properties now come from the FOAF vocabulary.
Expanding this document, uses a combination of terms defined in the outer context,
and those defined specifically for that term in a property-scoped context.
Scoping can also be performed using a term used as a value of @type:
Scoping on @type is useful when common properties are used to
relate things of different types, where the vocabularies in use within
different entities calls for different context scoping. For example,
hasPart/partOf may be common terms used in a document, but mean
different things depending on the context.
A type-scoped context is only in effect for the node object on which
the type is used; the previous in-scope contexts are placed back into
effect when traversing into another node object.
As described further in § 4.1.9 Context Propagation,
this may be controlled using the @propagate keyword.
The values of @type are unordered, so if multiple
types are listed, the order that type-scoped contexts are applied is based on
lexicographical ordering.
For example, consider the following semantically equivalent examples.
The first example, shows how properties and types can define their own
scoped contexts, which are included when expanding.
Example 47: Expansion using embedded and scoped contexts
Contexts are processed depending on how they are defined.
A property-scoped context is processed first,
followed by any embedded context,
followed lastly by the type-scoped contexts,
in the appropriate order. The previous example is logically equivalent to the following:
Example 48: Expansion using embedded and scoped contexts (embedding equivalent)
If a term defines a scoped context,
and then that term is later redefined,
the association of the context defined in the earlier
expanded term definition is lost
within the scope of that redefinition. This is consistent with
term definitions of a term overriding previous term definitions from
earlier less deeply nested definitions, as discussed in
§ 4.1 Advanced Context Usage.
Once introduced, contexts remain in effect until a subsequent
context removes it by setting @context to null,
or by redefining terms,
with the exception of type-scoped contexts,
which limit the effect of that context until the next node object is entered.
This behavior can be changed using the @propagate keyword.
The following example illustrates how terms defined in a context with @propagate set to false
are effectively removed when descending into new node object.
JSON-LD 1.0 included mechanisms for modifying the context that
is in effect. This included the capability to load and process a remote
context and then apply further changes to it via new contexts.
However, with the introduction of JSON-LD 1.1, it is also desirable to
be able to load a remote context, in particular an existing JSON-LD
1.0 context, and apply JSON-LD 1.1 features to it prior to
processing.
By using the @import keyword in a context, another remote
context, referred to as an imported context, can be loaded and
modified prior to processing. The modifications are expressed in the
context that includes the @import keyword, referred to as the
wrapping context. Once an imported context is loaded, the
contents of the wrapping context are merged into it prior to
processing. The merge operation will cause each key-value pair in the
wrapping context to be added to the loaded imported context,
with the wrapping context key-value pairs taking precedence.
By enabling existing contexts to be reused and edited inline prior
to processing, context-wide keywords can be applied to adjust all term
definitions in the imported context. Similarly, term definitions can
be replaced prior to processing, enabling adjustments that, for instance, ensure term
definitions match previously protected terms or that they include
additional type coercion information.
The following examples illustrate how @import can be used to express
a type-scoped context that loads an imported context and
sets @propagate to true, as a technique for making other similar modifications.
Suppose there was a context that could be referenced remotely
via the URL https://json-ld.org/contexts/remote-context.jsonld:
Example 50: A remote context to be imported in a type-scoped context
Similarly, the wrapping context may replace term definitions or
set other context-wide keywords that may affect how the imported
context term definitions will be processed:
Example 53: Sourcing a context to modify @vocab and a term definition
{
"@context": {
"@version": 1.1,
"@import": "https://json-ld.org/contexts/remote-context.jsonld",
"@vocab": "http://example.org/vocab#",
↑ This will replace any previous @vocab definition prior to processing it
"term1": {
"@id": "http://example.org/vocab#term1",
"@type": "http://www.w3.org/2001/XMLSchema#integer"
}
↑ This will replace the old term1 definition prior to processing it
}
}
Again, the effect would be the same as if the entire imported context
had been copied into the context:
Example 54: Result of sourcing a context to modify @vocab and a term definition
The result of loading imported contexts must be
context definition, not an IRI or an array.
Additionally, the imported context cannot include an @importentry.
4.1.11 Protected Term Definitions
This section is non-normative.
JSON-LD is used in many specifications as the specified data format.
However, there is also a desire to allow some JSON-LD contents to be processed as plain JSON,
without using any of the JSON-LD algorithms.
Because JSON-LD is very flexible,
some terms from the original format may be locally overridden
through the use of embedded contexts,
and take a different meaning for JSON-LD based implementations.
On the other hand, "plain JSON" implementations may not be able to interpret these embedded contexts,
and hence will still interpret those terms with their original meaning.
To prevent this divergence of interpretation,
JSON-LD 1.1 allows term definitions to be protected.
A protected term definition is a term definition with an entry@protected set to true.
It generally prevents further contexts from overriding this term definition,
either through a new definition of the same term,
or through clearing the context with "@context": null.
Such attempts will raise an error and abort the processing
(except in some specific situations described
below).
Example 55: A protected term definition can generally not be overridden
{
"@context": [
{
"@version": 1.1,
"Person": "http://xmlns.com/foaf/0.1/Person",
"knows": "http://xmlns.com/foaf/0.1/knows",
"name": {
"@id": "http://xmlns.com/foaf/0.1/name",
"@protected": true
}
},
{
– this attempt will fail with an error"name": "http://schema.org/name"
}
],
"@type": "Person",
"name": "Manu Sporny",
"knows": {
"@context": [
– this attempt would also fail with an errornull,
"http://schema.org/"
],
"name": "Gregg Kellogg"
}
}
When all or most term definitions of a context need to be protected,
it is possible to add an entry@protected set to true
to the context itself.
It has the same effect as protecting each of its term definitions individually.
Exceptions can be made by adding an entry@protected set to false
in some term definitions.
While protected terms can in general not be overridden,
there are two exceptions to this rule.
The first exception is that a context is allowed to redefine a protected term
if the new definition is identical to the protected term definition
(modulo the @protected flag).
The rationale is that the new definition does not violate the protection,
as it does not change the semantics of the protected term.
This is useful for widespread term definitions,
such as aliasing @type to type,
which may occur (including in a protected form) in several contexts.
The second exception is that a property-scoped context
is not affected by protection, and can therefore override protected terms,
either with a new term definition,
or by clearing the context with "@context": null.
The rationale is that "plain JSON" implementations,
relying on a given specification,
will only traverse properties defined by that specification.
Scoped contexts belonging to the specified properties are part of the specification,
so the "plain JSON" implementations are expected to be aware of the change of semantics they induce.
Scoped contexts belonging to other properties apply to parts of the document that "plain JSON" implementations will ignore.
In both cases, there is therefore no risk of diverging interpretations between JSON-LD-aware implementations and "plain JSON" implementations,
so overriding is permitted.
Note
By preventing terms from being overridden,
protection also prevents any adaptation of a term
(e.g., defining a more precise datatype, restricting the term's use to lists, etc.).
This kind of adaptation is frequent with some general purpose contexts,
for which protection would therefore hinder their usability.
As a consequence, context publishers should use this feature with care.
Note
Protected term definitions are a new feature in JSON-LD 1.1.
4.2 Describing Values
This section is non-normative.
Values are leaf nodes in a graph associated with scalar values such as
strings, dates, times, and other such atomic values.
4.2.1 Typed Values
This section is non-normative.
A value with an associated type, also known as a
typed value, is indicated by associating a value with
an IRI which indicates the value's type. Typed values may be
expressed in JSON-LD in three ways:
By utilizing the @typekeyword when defining
a term within an @context section.
By using a native JSON type such as number, true, or false.
The first example uses the @type keyword to associate a
type with a particular term in the @context:
The modified key's value above is automatically interpreted as a
dateTime value because of the information specified in the
@context. The example tabs show how a JSON-LD processor will interpret the data.
The second example uses the expanded form of setting the type information
in the body of a JSON-LD document:
Both examples above would generate the value
2010-05-29T14:17:39+02:00 with the type
http://www.w3.org/2001/XMLSchema#dateTime. Note that it is
also possible to use a term or a compact IRI to
express the value of a type.
A node type specifies the type of thing
that is being described, like a person, place, event, or web page. A
value type specifies the data type of a particular value, such
as an integer, a floating point number, or a date.
Example 61: Example demonstrating the context-sensitivity for @type
{
...
"@id": "http://example.org/posts#TripToWestVirginia",
"@type": "http://schema.org/BlogPosting", ← This is a node type
"http://purl.org/dc/terms/modified": {
"@value": "2010-05-29T14:17:39+02:00",
"@type": "http://www.w3.org/2001/XMLSchema#dateTime"← This is a value type
}
...
}
The first use of @type associates a node type
(http://schema.org/BlogPosting) with the node,
which is expressed using the @idkeyword.
The second use of @type associates a value type
(http://www.w3.org/2001/XMLSchema#dateTime) with the
value expressed using the @valuekeyword. As a
general rule, when @value and @type are used in
the same map, the @typekeyword is expressing a value type.
Otherwise, the @typekeyword is expressing a
node type. The example above expresses the following data:
4.2.2 JSON Literals
This section is non-normative.
At times, it is useful to include JSON within JSON-LD that is not interpreted as JSON-LD.
Generally, a JSON-LD processor will ignore properties which don't map to IRIs,
but this causes them to be excluded when performing various algorithmic transformations.
But, when the data that is being described is, itself, JSON, it's important that
it survives algorithmic transformations.
Warning
JSON-LD is intended to allow native JSON to be
interpreted through the use of a context.
The use of JSON literals creates blobs of data which are not available for interpretation.
It is for use only in the rare cases that JSON cannot be represented as JSON-LD.
When a term is defined with @type set to @json,
a JSON-LD processor will treat the value as a JSON literal,
rather than interpreting it further as JSON-LD.
In the expanded document form, such JSON will become the value of @value within a value object
having "@type": "@json".
The following example shows an example of a JSON Literal contained as the
value of a property. Note that the RDF results use a canonicalized form of the JSON
to ensure interoperability between different processors.
JSON canonicalization is described in Data Round Tripping in [JSON-LD11-API].
Note
Generally, when a JSON-LD processor encounters null,
the associated entry or value is removed.
However, null is a valid JSON token; when used as the value
of a JSON literal, a null value will be preserved.
4.2.3 Type Coercion
This section is non-normative.
JSON-LD supports the coercion of string values to particular data types.
Type coercion allows someone deploying JSON-LD to use string property values
and have those values be interpreted as typed values
by associating an IRI with the value in the expanded value object representation.
Using type coercion, string value representation can be used without requiring
the data type to be specified explicitly with each piece of data.
Type coercion is specified within an expanded term definition
using the @type key. The value of this key expands to an IRI.
Alternatively, the keyword@id or @vocab may be used
as value to indicate that within the body of a JSON-LD document, a string value of a
term coerced to @id or @vocab is to be interpreted as an
IRI. The difference between @id and @vocab is how values are expanded
to IRIs. @vocab first tries to expand the value
by interpreting it as term. If no matching term is found in the
active context, it tries to expand it as an IRI or a compact IRI
if there's a colon in the value; otherwise, it will expand the value using the
active context'svocabulary mapping, if present.
Values coerced to @id in contrast are expanded as
an IRI or a compact IRI if a colon is present; otherwise, they are interpreted
as relative IRI references.
Note
The ability to coerce a value using a term definition is distinct
from setting one or more types on a node object, as the former does not result in
new data being added to the graph, while the latter manages node types
through adding additional relationships to the graph.
Terms or compact IRIs used as the value of a
@type key may be defined within the same context. This means that one may specify a
term like xsd and then use xsd:integer within the same
context definition.
The example below demonstrates how a JSON-LD author can coerce values to
typed values and IRIs.
It is important to note that terms are only used in expansion
for vocabulary-relative positions, such as for keys and values of map entries.
Values of @id are considered to be document-relative,
and do not use term definitions for expansion. For example, consider the following:
The unexpected result is that "barney" expands to both http://example1.com/barney
and http://example2.com/barney, depending where it is encountered.
String values interpreted as IRIs because of the associated term definitions
are typically considered to be document-relative.
In some cases, it makes sense to interpret these relative to the vocabulary,
prescribed using "@type": "@vocab" in the term definition, though this can
lead to unexpected consequences such as these.
In the previous example, "barney" appears twice, once as the value of @id,
which is always interpreted as a document-relative IRI, and once as the value of
"fred", which is defined to be vocabulary-relative, thus the different expanded values.
A variation on the previous example using "@type": "@id" instead
of @vocab illustrates the behavior of interpreting "barney" relative to the document:
Note
The triple ex1:fred ex2:knows ex1:barney . is emitted twice,
but exists only once in an output dataset, as it is a duplicate triple.
Terms may also be defined using IRIs
or compact IRIs. This allows coercion rules
to be applied to keys which are not represented as a simple term.
For example:
In this case the @id definition in the term definition is optional.
If it does exist, the IRI or compact IRI representing
the term will always be expanded to IRI defined by the @id
key—regardless of whether a prefix is defined or not.
Type coercion is always performed using the unexpanded value of the key. In the
example above, that means that type coercion is done looking for foaf:age
in the active context and not for the corresponding, expanded
IRIhttp://xmlns.com/foaf/0.1/age.
Note
Keys in the context are treated as terms for the purpose of
expansion and value coercion. At times, this may result in multiple representations for the same expanded IRI.
For example, one could specify that dog and cat both expanded to http://example.com/vocab#animal.
Doing this could be useful for establishing different type coercion or language specification rules.
4.2.4 String Internationalization
This section is non-normative.
At times, it is important to annotate a string
with its language. In JSON-LD this is possible in a variety of ways.
First, it is possible to define a default language for a JSON-LD document
by setting the @language key in the context:
The example above would associate 忍者 with the specified default
language tag ja, Ninja with the language tag
en, and Nindža with the language tag cs.
The value of name, Yagyū Muneyoshi wouldn't be
associated with any language tag since @language was reset to
null in the expanded term definition.
Note
Language associations are only applied to plain
strings. Typed values
or values that are subject to type coercion
are not language tagged.
Just as in the example above, systems often need to express the value of a
property in multiple languages. Typically, such systems also try to ensure that
developers have a programmatically easy way to navigate the data structures for
the language-specific data. In this case, language maps
may be utilized.
Example 71: Language map expressing a property in three languages
The example above expresses exactly the same information as the previous
example but consolidates all values in a single property. To access the
value in a specific language in a programming language supporting dot-notation
accessors for object properties, a developer may use the
property.language pattern
(when languages are limited to the primary language sub-tag,
and do not depend on other sub-tags, such as "en-us").
For example, to access the occupation
in English, a developer would use the following code snippet:
obj.occupation.en.
The example above would associate the ar-EG language tag
and "rtl" base direction
with the two stringsHTML و CSS: تصميم و إنشاء مواقع الويب and مكتبة.
The default base direction applies to all
string values that are not type coerced.
To clear the default base direction for a subtree, @direction can
be set to null in an intervening context, such as a scoped context as follows:
A JSON-LD author can express multiple values in a compact way by using
arrays. Since graphs do not describe ordering for links
between nodes, arrays in JSON-LD do not convey any ordering of the
contained elements by default. This is exactly the opposite from regular JSON
arrays, which are ordered by default. For example, consider the following
simple document:
Multiple values may also be expressed using the expanded form:
Note
The example shown above would generates statement, again with
no inherent order.
Although multiple values of a property are typically of the same type,
JSON-LD places no restriction on this, and a property may have values
of different types:
Note
When viewed as statements, the values have no inherent order.
4.3.1 Lists
This section is non-normative.
As the notion of ordered collections is rather important in data
modeling, it is useful to have specific language support. In JSON-LD,
a list may be represented using the @listkeyword as follows:
This describes the use of this array as being ordered,
and order is maintained when processing a document. If every use of a given multi-valued
property is a list, this may be abbreviated by setting @container
to @list in the context:
The implementation of lists in RDF depends on linking anonymous nodes
together using the properties rdf:first and
rdf:rest, with the end of the list defined as the resource
rdf:nil, as the "statements" tab illustrates.
This allows order to be represented within an unordered set of statements.
Both JSON-LD and Turtle provide shortcuts for representing ordered lists.
In JSON-LD 1.1, lists of lists, where the value of
a list object, may itself be a list object, are
fully supported.
Note that the "@container": "@list" definition recursively
describes array values of lists as being, themselves, lists. For example, in The GeoJSON Format (see [RFC7946]),
coordinates are an ordered list of positions, which are
represented as an array of two or more numbers:
For these examples, it's important that values
expressed within bbox and coordinates maintain their order,
which requires the use of embedded list structures. In JSON-LD 1.1, we can
express this using recursive lists, by simply adding the appropriate context
definition:
Note that coordinates includes three levels of lists.
Values of terms associated with an @list container
are always represented in the form of an array,
even if there is just a single value or no value at all.
4.3.2 Sets
This section is non-normative.
While @list is used to describe ordered lists,
the @set keyword is used to describe unordered sets.
The use of @set in the body of a JSON-LD document
is optimized away when processing the document, as it is just syntactic
sugar. However, @set is helpful when used within the context
of a document.
Values of terms associated with an @set container
are always represented in the form of an array,
even if there is just a single value that would otherwise be optimized to
a non-array form in compact form (see
§ 5.2 Compacted Document Form). This makes post-processing of
JSON-LD documents easier as the data is always in array form, even if the
array only contains a single value.
This describes the use of this array as being unordered,
and order may change when processing a document. By default,
arrays of values are unordered, but this may be made explicit by
setting @container to @set in the context:
Since JSON-LD 1.1, the @set keyword may be
combined with other container specifications within an expanded term
definition to similarly cause compacted values of indexes to be consistently
represented using arrays. See § 4.6 Indexed Values for a further discussion.
Many JSON APIs separate properties from their entities using an
intermediate object; in JSON-LD these are called nested properties.
For example, a set of possible labels may be grouped
under a common property:
By defining labels using the keyword@nest,
a JSON-LD processor will ignore the nesting created by using the
labels property and process the contents as if it were declared
directly within containing object. In this case, the labels
property is semantically meaningless. Defining it as equivalent to
@nest causes it to be ignored when expanding, making it
equivalent to the following:
Similarly, term definitions may contain a @nest property
referencing a term aliased to @nest which will cause such
properties to be nested under that aliased term when compacting.
In the example below, both main_label and other_label are defined
with "@nest": "labels", which will cause them to be serialized under
labels when compacting.
Example 90: Defining property nesting - Expanded Input
[{
"@id": "http://example.org/myresource",
"http://xmlns.com/foaf/0.1/homepage": [
{"@id": "http://example.org"}
],
"http://www.w3.org/2004/02/skos/core#prefLabel": [
{"@value": "This is the main label for my resource"}
],
"http://www.w3.org/2004/02/skos/core#altLabel": [
{"@value": "This is the other label"}
]
}]
Embedding is a JSON-LD feature that allows an author to
use node objects as
property values. This is a commonly used mechanism for
creating a parent-child relationship between two nodes.
Without embedding, node objects can be linked by referencing the
identifier of another node object. For example:
The previous example describes two node objects, for Manu and Gregg, with
the knows property defined to treat string values as identifiers.
Embedding allows the node object for Gregg to be embedded as a value
of the knows property:
A node object, like the one used above, may be used in
any value position in the body of a JSON-LD document.
While it is considered a best practice to identify nodes in a graph,
at times this is impractical. In the data model, nodes without an explicit
identifier are called blank nodes, which can be represented in a
serialization such as JSON-LD using a blank node identifier. In the
previous example, the top-level node for Manu does not have an identifier,
and does not need one to describe it within the data model. However, if we
were to want to describe a knows relationship from Gregg to Manu,
we would need to introduce a blank node identifier
(here _:b0).
Blank node identifiers may be automatically introduced by algorithms such as flattening, but they are also useful for authors to describe such relationships directly.
4.5.1 Identifying Blank Nodes
This section is non-normative.
At times, it becomes necessary to be able to express information without
being able to uniquely identify the node with an IRI.
This type of node is called a blank node. JSON-LD does not require
all nodes to be identified using @id. However, some graph topologies
may require identifiers to be serializable. Graphs containing loops, e.g., cannot
be serialized using embedding alone, @id must be used to connect the nodes.
In these situations, one can use blank node identifiers,
which look like IRIs using an underscore (_)
as scheme. This allows one to reference the node locally within the document, but
makes it impossible to reference the node from an external document. The
blank node identifier is scoped to the document in which it is used.
The example above contains information about two secret agents that cannot be identified
with an IRI. While expressing that agent 1 knows agent 2
is possible without using blank node identifiers,
it is necessary to assign agent 1 an identifier so that it can be referenced
from agent 2.
It is worth noting that blank node identifiers may be relabeled during processing.
If a developer finds that they refer to the blank node more than once,
they should consider naming the node using a dereferenceable IRI so that
it can also be referenced from other documents.
4.6 Indexed Values
This section is non-normative.
Sometimes multiple property values need to be accessed
in a more direct fashion than iterating though multiple array values. JSON-LD
provides an indexing mechanism to allow the use of an intermediate map
to associate specific indexes with associated values.
Data Indexing
As described in § 4.6.1 Data Indexing,
data indexing allows an arbitrary key to reference a node or value.
Language Indexing
As described in § 4.6.2 Language Indexing,
language indexing allows a language to reference a string and be
interpreted as the language associated with that string.
Databases are typically used to make access to
data more efficient. Developers often extend this sort of functionality into
their application data to deliver similar performance gains.
This data may have no meaning from a Linked Data standpoint, but is
still useful for an application.
JSON-LD introduces the notion of index maps
that can be used to structure data into a form that is
more efficient to access. The data indexing feature allows an author to
structure data using a simple key-value map where the keys do not map
to IRIs. This enables direct access to data
instead of having to scan an array in search of a specific item.
In JSON-LD such data can be specified by associating the
@indexkeyword with a
@container declaration in the context:
In the example above, the athletesterm has
been marked as an index map.
The catcher and pitcher keys will be ignored semantically,
but preserved syntactically, by the JSON-LD Processor.
If used in JavaScript, this can allow a developer to access a particular athlete using the
following code snippet: obj.athletes.pitcher.
As data indexes are not preserved when round-tripping to RDF;
this feature should be used judiciously.
Often, other indexing mechanisms, which are preserved, are more appropriate.
The value of @container can also
be an array containing both @index and @set.
When compacting, this ensures that a JSON-LD Processor will use
the array form for all values of indexes.
Unless the processing mode is set to json-ld-1.0,
the special index @none is used for indexing
data which does not have an associated index, which is useful to maintain
a normalized representation.
4.6.1.1 Property-based data indexing
This section is non-normative.
In its simplest form (as in the examples above),
data indexing assigns no semantics to the keys of an index map.
However, in some situations,
the keys used to index objects are semantically linked to these objects,
and should be preserved not only syntactically, but also semantically.
Unless the processing mode is set to json-ld-1.0,
"@container": "@index" in a term description can be accompanied with
an "@index" key. The value of that key must map to an IRI,
which identifies the semantic property linking each object to its key.
JSON which includes string values in multiple languages may be
represented using a language map to allow for easily
indexing property values by language tag. This enables direct access to
language values instead of having to scan an array in search of a specific item.
In JSON-LD such data can be specified by associating the
@languagekeyword with a
@container declaration in the context:
In the example above, the labelterm has
been marked as a language map. The en and
de keys are implicitly associated with their respective
values by the JSON-LD Processor. This allows a developer to
access the German version of the label using the
following code snippet: obj.label.de,
which, again, is only appropriate when languages are limited to the
primary language sub-tag and do not depend on other sub-tags, such as "de-at".
The value of @container can also
be an array containing both @language and @set.
When compacting, this ensures that a JSON-LD Processor will use
the array form for all values of language tags.
Unless the processing mode is set to json-ld-1.0,
the special index @none is used for indexing
strings which do not have a language; this is useful to maintain
a normalized representation for string values not having a datatype.
4.6.3 Node Identifier Indexing
This section is non-normative.
In addition to index maps, JSON-LD introduces the notion of id maps
for structuring data. The id indexing feature allows an author to
structure data using a simple key-value map where the keys map
to IRIs. This enables direct access to associated node objects
instead of having to scan an array in search of a specific item.
In JSON-LD such data can be specified by associating the
@idkeyword with a
@container declaration in the context:
In the example above, the postterm has
been marked as an id map. The http://example.com/posts/1/en and
http://example.com/posts/1/de keys will be interpreted
as the @id property of the node object value.
The value of @container can also
be an array containing both @id and @set.
When compacting, this ensures that a JSON-LD processor will use
the array form for all values of node identifiers.
The special index @none is used for indexing
node objects which do not have an @id, which is useful to maintain
a normalized representation. The @none index may also be
a term which expands to @none, such as the term none
used in the example below.
In addition to id and index maps, JSON-LD introduces the notion of type maps
for structuring data. The type indexing feature allows an author to
structure data using a simple key-value map where the keys map
to IRIs. This enables data to be structured based on the @type
of specific node objects.
In JSON-LD such data can be specified by associating the
@typekeyword with a
@container declaration in the context:
In the example above, the affiliationterm has
been marked as a type map. The schema:Corporation and
schema:ProfessionalService keys will be interpreted
as the @type property of the node object value.
The value of @container can also
be an array containing both @type and @set.
When compacting, this ensures that a JSON-LD processor will use
the array form for all values of types.
The special index @none is used for indexing
node objects which do not have an @type, which is useful to maintain
a normalized representation. The @none index may also be
a term which expands to @none, such as the term none
used in the example below.
As with id maps, when used with @type, a container may also
include @set to ensure that key values are always contained in an array.
Sometimes it is also useful to list node objects as part of another node object.
For instance, to represent a set of resources which are used by some other
resource. Included blocks may be also be used to collect such secondary node objects
which can be referenced from a primary node object.
For an example, consider a node object containing a list of different items,
some of which share some common elements:
When flattened, this will move the employee and contractor elements
from the included block into the outer array.
Included resources are described in
Inclusion of Related Resources of JSON API [JSON.API]
as a way to include related resources associated with some primary resource;
@included provides an analogous possibility in JSON-LD.
As a by product of the use of @included within node objects, a map may contain
only @included, to provide a feature similar to that described in § 4.1 Advanced Context Usage,
where @graph is used to described disconnected nodes.
However, in contrast to @graph, @included does not interact with other properties
contained within the same map, a feature discussed further in § 4.9 Named Graphs.
4.8 Reverse Properties
This section is non-normative.
JSON-LD serializes directed graphs. That means that
every property points from a node to another node
or value. However, in some cases, it is desirable
to serialize in the reverse direction. Consider for example the case where a person
and its children should be described in a document. If the used vocabulary does not
provide a childrenproperty but just a parentproperty, every node representing a child would have to
be expressed with a property pointing to the parent as in the following
example.
Expressing such data is much simpler by using JSON-LD's @reversekeyword:
The @reversekeyword can also be used in
expanded term definitions
to create reverse properties as shown in the following example:
4.9 Named Graphs
This section is non-normative.
At times, it is necessary to make statements about a graph
itself, rather than just a single node. This can be done by
grouping a set of nodes using the @graphkeyword. A developer may also name data expressed using the
@graphkeyword by pairing it with an
@idkeyword as shown in the following example:
The example above expresses a named graph that is identified
by the IRIhttp://example.org/foaf-graph. That
graph is composed of the statements about Manu and Gregg. Metadata about
the graph itself is expressed via the generatedAt property,
which specifies when the graph was generated.
When a JSON-LD document's top-level structure is a
map that contains no other
keys than @graph and
optionally @context (properties that are not mapped to an
IRI or a keyword are ignored),
@graph is considered to express the otherwise implicit
default graph. This mechanism can be useful when a number
of nodes exist at the document's top level that
share the same context, which is, e.g., the case when a
document is flattened. The
@graph keyword collects such nodes in an array
and allows the use of a shared context.
In this case, embedding can not be used as
the graph contains unrelated nodes.
This is equivalent to using multiple
node objects in array and defining
the @context within each node object:
4.9.1 Graph Containers
This section is non-normative.
In some cases, it is useful to logically partition data into separate
graphs, without making this explicit within the JSON expression. For
example, a JSON document may contain data against which other metadata is
asserted and it is useful to separate this data in the data model using
the notion of named graphs, without the syntactic overhead
associated with the @graph keyword.
A different example uses an anonymously named graph as follows:
The example above expresses an anonymously named graph
making a statement. The default graph includes a statement
saying that the subject wrote that statement.
This is an example of separating statements into a named graph, and then
making assertions about the statements contained within that named graph.
Graph Containers are a new feature in JSON-LD 1.1.
4.9.2 Named Graph Data Indexing
This section is non-normative.
In addition to indexing node objects by index, graph objects may
also be indexed by an index. By using the @graph
container type, introduced in § 4.9.1 Graph Containers
in addition to @index, an object value of such a property is
treated as a key-value map where the keys do not map to IRIs, but
are taken from an @index property associated with named graphs
which are their values. When expanded, these must be simple graph objects
The following example describes a default graph referencing multiple named
graphs using an index map.
As with index maps, when used with @graph, a container may also
include @set to ensure that key values are always contained in an array.
The special index @none is used for indexing
graphs which do not have an @index key, which is useful to maintain
a normalized representation. Note, however, that
compacting a document where multiple unidentified named graphs are
compacted using the @none index will result in the content
of those graphs being merged. To prevent this, give each graph a distinct
@index key.
Note
Named Graph Data Indexing is a new feature in JSON-LD 1.1.
4.9.3 Named Graph Indexing
This section is non-normative.
In addition to indexing node objects by identifier, graph objects may
also be indexed by their graph name. By using the @graph
container type, introduced in § 4.9.1 Graph Containers
in addition to @id, an object value of such a property is
treated as a key-value map where the keys represent the identifiers of named graphs
which are their values.
The following example describes a default graph referencing multiple named
graphs using an id map.
As with id maps, when used with @graph, a container may also
include @set to ensure that key values are always contained in an array.
As with id maps, the special index @none is used for indexing
named graphs which do not have an @id, which is useful to maintain
a normalized representation. The @none index may also be
a term which expands to @none.
Note, however, that if multiple graphs are represented without
an @id, they will be merged on expansion. To prevent this,
use @none judiciously, and consider giving graphs
their own distinct identifier.
Note
Graph Containers are a new feature in JSON-LD 1.1.
4.10 Loading Documents
This section is non-normative.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API]
defines the interface to a JSON-LD Processor and includes
a number of methods used for manipulating different forms
of JSON-LD (see § 5. Forms of JSON-LD).
This includes a general mechanism for loading remote documents,
including referenced JSON-LD documents and remote contexts,
and potentially extracting embedded JSON-LD from other formats such as [HTML].
This is more fully described in
Remote Document and Context Retrieval
in [JSON-LD11-API].
A documentLoader
can be useful in a number of contexts where loading remote documents can be problematic:
Remote context documents should be cached to prevent overloading the
location of the remote context for each request.
Normally, an HTTP caching infrastructure might be expected to handle this,
but in some contexts this might not be feasible.
A documentLoader implementation might provide separate logic for performing
such caching.
Non-standard URL schemes may not be widely implemented,
or may have behavior specific to a given application domain.
A documentLoader can be defined to implement document retrieval semantics.
Certain well-known contexts may be statically cached within a documentLoader implementation.
This might be particularly useful in embedded applications,
where it is not feasible, or even possible, to access remote documents.
For security purposes, the act of remotely retrieving a document may provide a signal of application behavior.
The judicious use of a documentLoader can isolate the application and reduce its online fingerprint.
5. Forms of JSON-LD
This section is non-normative.
As with many data formats, there is no single correct way to describe data in JSON-LD.
However, as JSON-LD is used for describing graphs, certain transformations can be used
to change the shape of the data, without changing its meaning as Linked Data.
Expanded Document Form
Expansion is the process of taking a JSON-LD document and applying a
context so that the @context is no longer necessary.
This process is described further in § 5.1 Expanded Document Form.
Flattening is the process of extracting
embedded nodes to the top level of the JSON tree, and replacing the embedded
node with a reference, creating blank node identifiers as necessary. This
process is described further in § 5.3 Flattened Document Form.
Framed Document Form
Framing is used to shape
the data in a JSON-LD document, using an example frame document
which is used to both match the flattened data and show an example
of how the resulting data should be shaped. This
process is described further in § 5.4 Framed Document Form.
5.1 Expanded Document Form
This section is non-normative.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API]
defines a method for expanding a JSON-LD document.
Expansion is the process of taking a JSON-LD document and applying a
context such that all IRIs, types, and values
are expanded so that the @context is no longer necessary.
For example, assume the following JSON-LD input document:
Example 123: Sample JSON-LD document to be expanded
Running the JSON-LD Expansion algorithm against the JSON-LD input document
provided above would result in the following output:
JSON-LD's media type defines a
profile parameter which can be used to signal or request
expanded document form. The profile URI identifying
expanded document form is http://www.w3.org/ns/json-ld#expanded.
5.2 Compacted Document Form
This section is non-normative.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API] defines
a method for compacting a JSON-LD document. Compaction is the process
of applying a developer-supplied context to shorten IRIs
to terms or compact IRIs
and JSON-LD values expressed in expanded form to simple values such as
strings or numbers.
Often this makes it simpler to work with document as the data is expressed in
application-specific terms. Compacted documents are also typically easier to read
for humans.
For example, assume the following JSON-LD input document:
Running the JSON-LD Compaction algorithm given the context supplied above
against the JSON-LD input document provided above would result in the following
output:
JSON-LD's media type defines a
profile parameter which can be used to signal or request
compacted document form. The profile URI identifying
compacted document form is http://www.w3.org/ns/json-ld#compacted.
The details of Compaction are described in the
Compaction algorithm in [JSON-LD11-API].
This section provides a short description of how the algorithm operates as a guide
to authors creating contexts to be used for compacting JSON-LD documents.
The purpose of compaction is to apply the term definitions, vocabulary mapping, default language,
and base IRI to an existing JSON-LD document to cause it to be represented in a form
that is tailored to the use of the JSON-LD document directly as JSON.
This includes representing values as strings, rather than value objects, where possible,
shortening the use of list objects into simple arrays, reversing the relationship
between nodes, and using data maps to index into multiple values instead of
representing them as an array of values.
The vocabulary mapping can be used to shorten IRIs that may be vocabulary relative
by removing the IRI prefix that matches the vocabulary mapping.
This is done whenever an IRI is determined to be vocabulary relative,
i.e., used as a property, or a value of @type,
or as the value of a term described as "@type": "@vocab".
5.2.2 Representing Values as Strings
This section is non-normative.
To be unambiguous, the expanded document form always represents nodes
and values using node objects and value objects.
Moreover, property values are always contained within an array, even when there is only
one value. Sometimes this is useful to maintain a uniformity of access,
but most JSON data use the simplest possible representation, meaning that
properties have single values, which are represented as strings
or as structured values such as node objects.
By default, compaction will represent values which are simple strings as strings,
but sometimes a value is an IRI, a date, or some other typed value for which
a simple string representation would loose information.
By specifying this within a term definition,
the semantics of a string value can be inferred from the definition
of the term used as a property.
See § 4.2 Describing Values for more details.
5.2.3 Representing Lists as Arrays
This section is non-normative.
As described in § 4.3.1 Lists,
JSON-LD has an expanded syntax for representing ordered values,
using the @list keyword.
To simplify the representation in JSON-LD, a term can be defined with
"@container": "@list" which causes all values of a
property using such a term to be considered ordered.
5.2.4 Reversing Node Relationships
This section is non-normative.
In some cases, the property used to relate two nodes may
be better expressed if the nodes have a reverse direction,
for example, when describing a relationship between
two people and a common parent.
See § 4.8 Reverse Properties for more details.
Reverse properties can be even more useful when combined with
framing, which can actually make node objects defined
at the top-level of a document to become embedded nodes.
JSON-LD provides a means to index such values, by defining
an appropriate @container definition within a term definition.
5.2.5 Indexing Values
This section is non-normative.
Properties with multiple values are typically represented using
an unordered array. This means that an application working
on an internalized representation of that JSON would need to
iterate through the values of the array to find a value matching
a particular pattern, such as a language-tagged string
using the language en.
Data can be indexed on a number of different keys, including
@id, @type, @language, @index and more.
See § 4.6 Indexed Values and
§ 4.9 Named Graphs for more details.
5.2.6 Normalizing Values as Objects
This section is non-normative.
Sometimes it's useful to compact a document, but keep the
node object and value object representations.
For this, a term definition can set "@type": "@none".
This causes the Value Compaction algorithm to always use the object
form of values, although components of that value may be compacted.
5.2.7 Representing Singular Values as Arrays
This section is non-normative.
Generally, when compacting, properties having only one value are
represented as strings or maps, while properties having
multiple values are represented as an array of strings or maps.
This means that applications accessing such properties need to be prepared
to accept either representation. To force all values to be represented
using an array, a term definition can set "@container": "@set".
Moreover, @set can be used in combination with other container settings,
for example looking at our language-map example from § 5.2.5 Indexing Values:
5.2.8 Term Selection
This section is non-normative.
When compacting, the Compaction algorithm will compact using a term
for a property only when the values of that property match the
@container, @type, and @language specifications for that term definition.
This can actually split values between different properties, all of which
have the same IRI. In case there is no matching term definition,
the compaction algorithm will compact using the absolute IRI of the property.
5.3 Flattened Document Form
This section is non-normative.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API] defines
a method for flattening a JSON-LD document.
Flattening collects all
properties of a node in a single map and labels
all blank nodes with
blank node identifiers.
This ensures a shape of the data and consequently may drastically simplify the code
required to process JSON-LD in certain applications.
For example, assume the following JSON-LD input document:
Example 137: Sample JSON-LD document to be flattened
Running the JSON-LD Flattening algorithm against the JSON-LD input document in
the example above and using the same context would result in the following
output:
The JSON-LD 1.1 Framing specification [JSON-LD11-FRAMING] defines
a method for framing a JSON-LD document. Framing is used to shape
the data in a JSON-LD document, using an example frame document
which is used to both match the flattened data and show an example
of how the resulting data should be shaped.
This frame document describes an embedding structure that would place
objects with type Library at the top, with objects of
type Book that were linked to the library object using
the contains property embedded as property values. It also
places objects of type Chapter within the referencing Book object
as embedded values of the Book object.
When using a flattened set of objects that match the frame components:
The Frame Algorithm can create a new document which follows the structure
of the frame:
JSON-LD's media type defines a
profile parameter which can be used to signal or request
framed document form. The profile URI identifying
framed document form is http://www.w3.org/ns/json-ld#framed.
JSON-LD's media type also defines a
profile parameter which can be used to identify a
script element in an HTML document containing a frame.
The first script element
of type application/ld+json;profile=http://www.w3.org/ns/json-ld#frame
will be used to find a frame..
6. Modifying Behavior with Link Relationships
Certain aspects of JSON-LD processing can be modified using
HTTP Link Headers [RFC8288].
These can be used when retrieving resources that are not, themselves, JSON-LD,
but can be interpreted as JSON-LD by using information in a
Link Relation.
In other cases, a resource may be returned using a representation that cannot easily be interpreted
as JSON-LD. Normally, HTTP content negotiation
would be used to allow a client to specify a preference for JSON-LD over another representation,
but in certain situations, it is not possible or practical for a server to respond appropriately to such requests.
For this, an HTTP Link Header can be used to provide an alternate location for a document
to be used in place of the originally requested resource,
as described in § 6.2 Alternate Document Location.
6.1 Interpreting JSON as JSON-LD
Ordinary JSON documents can be interpreted as JSON-LD
by providing an explicit JSON-LD context document. One way
to provide this is by using referencing a JSON-LD
context document in an HTTP Link Header.
Doing so allows JSON to be unambiguously machine-readable without requiring developers to drastically
change their documents and provides an upgrade path for existing infrastructure
without breaking existing clients that rely on the application/json
media type or a media type with a +json suffix as defined in
[RFC6839].
In order to use an external context with an ordinary JSON document,
when retrieving an ordinary JSON document via HTTP, processors MUST
attempt to retrieve any JSON-LD document referenced by a
Link Header with:
rel="http://www.w3.org/ns/json-ld#context", and
type="application/ld+json".
The referenced document MUST have a top-level JSON object.
The @contextentry within that object is added to the top-level
JSON object of the referencing document. If an array
is at the top-level of the referencing document and its items are
JSON objects, the @context
subtree is added to all array items. All extra information located outside
of the @context subtree in the referenced document MUST be
discarded. Effectively this means that the active context is
initialized with the referenced external context. A response MUST NOT
contain more than one HTTP Link Header using the
http://www.w3.org/ns/json-ld#context link relation.
Other mechanisms for providing a JSON-LD Context MAY be described for other
URI schemes.
The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API]
provides for an expandContext option for specifying
a context to use when expanding JSON documents programmatically.
The following example demonstrates the use of an external context with an
ordinary JSON document over HTTP:
Example 142: Referencing a JSON-LD context from a JSON document via an HTTP Link Header
Please note that JSON-LD documents
served with the application/ld+json
media type MUST have all context information, including references to external
contexts, within the body of the document. Contexts linked via a
http://www.w3.org/ns/json-ld#contextHTTP Link HeaderMUST be
ignored for such documents.
6.2 Alternate Document Location
Documents which can't be directly interpreted as JSON-LD can provide an alternate location containing JSON-LD.
One way to provide this is by referencing a JSON-LD document in an HTTP Link Header.
This might be useful, for example, when the URL associated with a namespace naturally
contains an HTML document, but the JSON-LD context associated with that URL is located elsewhere.
To specify an alternate location, a non-JSON resource
(i.e., one using a media type other than application/json or a derivative)
can return the alternate location using a Link Header with:
rel="alternate", and
type="application/ld+json".
A response MUST NOT contain more than one HTTP Link Header using the
alternate link relation with type="application/ld+json" .
Other mechanisms for providing an alternate location MAY be described for other
URI schemes.
The following example demonstrates the use of an alternate location with an
ordinary HTTP document over HTTP:
Example 143: Specifying an alternate location via an HTTP Link Header
GET /index.html HTTP/1.1
Host: example.com
Accept: application/ld+json,application/json,*/*;q=0.1
====================================
HTTP/1.1 200 OK
...
Content-Type: text/htmlLink: <alternate.jsonld>; rel="alternate"; type="application/ld+json"
<html>
<head>
<title>Primary Entrypoint</title>
</head>
<body>
<p>This is the primary entrypoint for a vocabulary</p>
</body>
</html>
A processor seeing a non-JSON result will note the presence of the link header
and load that document instead.
JSON-LD content can be easily embedded in HTML [HTML] by placing
it in a script element with the type attribute set to
application/ld+json. Doing so creates a
data block.
Defining how such data may be used is beyond the scope of this specification.
The embedded JSON-LD document might be extracted as is or, e.g., be
interpreted as RDF.
When processing a JSON-LD
script element,
the Document Base URL
of the containing HTML document,
as defined in [HTML],
is used to establish the default base IRI of the enclosed
JSON-LD content.
HTML allows for Dynamic changes to base URLs.
This specification does not require any specific behavior,
and to ensure that all systems process the base IRI equivalently, authors SHOULD
either use IRIs, or explicitly as defined in § 4.1.3 Base IRI.
Implementations (particularly those natively operating in the [DOM]) MAY take into consideration
Dynamic changes to base URLs.
7.2 Restrictions for contents of JSON-LD script elements
Authors should avoid using character sequences in scripts embedded in HTML
which may be confused with a comment-open, script-open,
comment-close, or script-close.
Note
Such content should be escaped as indicated below, however
the content will remain escaped after processing through the
JSON-LD API [JSON-LD11-API].
A specific
script element
within an HTML document may be located using
a fragment identifier matching the unique identifier
of the script element within the HTML document located by a URL (see [DOM]).
A JSON-LD processorMUST extract only the specified data block's contents
parsing it as a standalone JSON-LD document
and MUST NOT merge the result with any other markup from the same HTML document.
For example, given an HTML document located at http://example.com/document,
a script element identified by "dave" can be targeted using the URL
http://example.com/document#dave.
8. Data Model
JSON-LD is a serialization format for Linked Data based on JSON.
It is therefore important to distinguish between the syntax, which is
defined by JSON in [RFC8259], and the data model which is
an extension of the RDF data model [RDF11-CONCEPTS].
The precise details of how JSON-LD relates to the RDF data model are given in
§ 10. Relationship to RDF.
To ease understanding for developers unfamiliar with the RDF model, the
following summary is provided:
A graph
is a labeled directed graph, i.e., a set of nodes
connected by directed-arcs.
Every directed-arc is labeled with
an IRI or a blank node identifier. Within the JSON-LD syntax
these arc labels are called properties.
Whenever practical, a directed-arc SHOULD be labeled with an IRI.
Note
The use of blank node identifiers to label properties is obsolete,
and may be removed in a future version of JSON-LD.
Consider using a document-relative IRI, instead, such as #.
Every node
is an IRI, a blank node, or a literal,
although syntactically lists and native JSON values may be represented directly.
This effectively just prohibits unnested, empty node objects
and unnested node objects that contain only an @id.
A document may have nodes which are unrelated, as long as one or more
properties are defined, or the node is referenced from another node object.
An IRI (Internationalized Resource Identifier) is a string that conforms to the syntax
defined in [RFC3987]. IRIs used within a
graphSHOULD return a Linked Data document describing
the resource denoted by that IRI when being dereferenced.
JSON-LD documentsMAY contain data
that cannot be represented by the data model
defined above. Unless otherwise specified, such data is ignored when a
JSON-LD document is being processed. One result of this rule
is that properties which are not mapped to an IRI,
a blank node, or keyword will be ignored.
The dataset described in this figure can be represented as follows:
Note
Note the use of @graph at the outer-most level to describe three top-level
resources (two of them named graphs). The named graphs use @graph in addition
to @id to provide the name for each graph.
9. JSON-LD Grammar
This section restates the syntactic conventions described in the
previous sections more formally.
In contrast to JSON, in JSON-LD the keys in objectsMUST be unique.
Whenever a keyword is discussed in this grammar,
the statements also apply to an alias for that keyword.
Note
JSON-LD allows keywords to be aliased
(see § 4.1.6 Aliasing Keywords for details). For example, if the active context
defines the termid as an alias for @id,
that alias may be legitimately used as a substitution for @id.
Note that keyword aliases are not expanded during context
processing.
A termMUST NOT equal any of the JSON-LD keywords,
other than @type.
When used as the prefix in a Compact IRI, to avoid
the potential ambiguity of a prefix being confused with an IRI
scheme, termsSHOULD NOT come from the list of URI schemes as defined in
[IANA-URI-SCHEMES]. Similarly, to avoid confusion between a
Compact IRI and a term, terms SHOULD NOT include a colon (:)
and SHOULD be restricted to the form of
isegment-nz-nc
as defined in [RFC3987].
To avoid forward-compatibility issues, a termSHOULD NOT start
with an @ character
followed exclusively by one or more ALPHA characters (see [RFC5234])
as future versions of JSON-LD may introduce
additional keywords. Furthermore, the term MUST NOT
be an empty string ("") as not all programming languages
are able to handle empty JSON keys.
The properties of a node in
a graph may be spread among different
node objects within a document. When
that happens, the keys of the different
node objects need to be merged to create the
properties of the resulting node.
If the node object contains the @graph
key, its value MUST be
a node object or
an array of zero or more node objects.
If the node object also contains an @id keyword,
its value is used as the graph name of a named graph.
See § 4.9 Named Graphs for further discussion on
@graph values. As a special case, if a map
contains no keys other than @graph and @context, and the
map is the root of the JSON-LD document, the
map is not treated as a node object; this
is used as a way of defining node objects
that may not form a connected graph. This allows a
context to be defined which is shared by all of the constituent
node objects.
Keys in a node object that are not
keywordsMAY expand to an IRI
using the active context. The values associated with keys that expand
to an IRIMUST be one of the following:
A frame objectMAY include a default object as the value of any key
which is not a keyword.
Values of @defaultMAY include the value @null,
or an array containing only @null, in addition to other values
allowed in the grammar for values of entry keys expanding to IRIs.
A graph object represents a named graph, which MAY include
an explicit graph name.
A map is a graph object if
it exists outside of a JSON-LD context,
it contains an @graphentry (or an alias of that keyword),
it is not the top-most map in the JSON-LD document, and
it consists of no entries other than @graph,
@index, @id
and @context, or an alias of one of these keywords.
A value objectMUST be a map containing the
@value key. It MAY also contain an @type,
an @language,
an @direction,
an @index, or an @context key but MUST NOT contain
both an @type and either @languageor @direction
keys at the same time.
A value objectMUST NOT contain any other keys that expand to an
IRI or keyword.
The value associated with the @value key MUST be either a
string, a number, true,
false or null.
If the value associated with the @type key
is @json, the value MAY be either an array or an object.
The values of
@value,
@language,
@direction and
@typeMAY additionally be
an empty map (wildcard),
an array containing only an empty map,
an empty array (match none),
an array of strings.
9.7 Lists and Sets
A list represents an ordered set of values. A set
represents an unordered set of values. Unless otherwise specified,
arrays are unordered in JSON-LD. As such, the
@set keyword, when used in the body of a JSON-LD document,
represents just syntactic sugar which is optimized away when processing the document.
However, it is very helpful when used within the context of a document. Values
of terms associated with an @set or @list container
will always be represented in the form of an array when a document
is processed—even if there is just a single value that would otherwise be optimized to
a non-array form in compacted document form.
This simplifies post-processing of the data as the data is always in a
deterministic form.
A list objectMUST be a map that contains no
keys that expand to an IRI or keyword other
than @list and @index.
A set objectMUST be a map that contains no
keys that expand to an IRI or keyword other
than @set and @index.
Please note that the @index key will be ignored when being processed.
In both cases, the value associated with the keys @list and @setMUST be one of the following types:
A language map is used to associate a language with a value in a
way that allows easy programmatic access. A language map may be
used as a term value within a node object if the term is defined
with @container set to @language,
or an array containing both @language and @set. The keys of a
language mapMUST be strings representing
[BCP47] language tags, the keyword@none,
or a term which expands to @none,
and the values MUST be any of the following types:
An index map allows keys that have no semantic meaning,
but should be preserved regardless, to be used in JSON-LD documents.
An index map may
be used as a term value within a node object if the
term is defined with @container set to @index,
or an array containing both @index and @set.
The values of the entries of an index mapMUST be one
of the following types:
Index Maps may also be used to map indexes to associated
named graphs, if the term is defined with @container
set to an array containing both @graph and
@index, and optionally including @set. The
value consists of the node objects contained within the named
graph which is indexed using the referencing key, which can be
represented as a simple graph object if the value does
not include @id, or a named graph if it includes @id.
9.10 Property-based Index Maps
A property-based index map is a variant of index map
were indexes are semantically preserved in the graph as property values.
A property-based index map may be used as a term value within a node object
if the term is defined with @container set to @index,
or an array containing both @index and @set,
and with @index set to a string.
The values of a property-based index mapMUST be node objects
or strings which expand to node objects.
When expanding,
if the active context contains a term definition
for the value of @index,
this term definition will be used to expand the keys of the index map.
Otherwise, the keys will be expanded as simple value objects.
Each node object in the expanded values of the index map
will be added an additional property value,
where the property is the expanded value of @index,
and the value is the expanded referencing key.
If the value contains a property expanding to @id, its value MUST
be equivalent to the referencing key. Otherwise, the property from the value is used as
the @id of the node object value when expanding.
Id Maps may also be used to map graph names to their
named graphs, if the term is defined with @container
set to an array containing both @graph and @id,
and optionally including @set. The value consists of the
node objects contained within the named graph
which is named using the referencing key.
If the value contains a property expanding to @type, and its value
is contains the referencing key after suitable expansion of both the referencing key
and the value, then the node object already contains the type. Otherwise, the property from the value is
added as a @type of the node object value when expanding.
A nested property is used to gather properties of a node object in a separate
map, or array of maps which are not
value objects. It is semantically transparent and is removed
during the process of expansion. Property nesting is recursive, and
collections of nested properties may contain further nesting.
Semantically, nesting is treated as if the properties and values were declared directly
within the containing node object.
An expanded term definition is used to describe the mapping
between a term and its expanded identifier, as well as other
properties of the value associated with the term when it is
used as key in a node object.
An expanded term definitionMUST be a map
composed of zero or more keys from
@id,
@reverse,
@type,
@language,
@container,
@context,
@prefix,
@propagate, or
@protected.
An expanded term definitionSHOULD NOT contain any other keys.
When the associated term is @type, the expanded term definitionMUST NOT contain keys other than @container and @protected.
The value of @container is limited to the single value @set.
If the expanded term definition contains the @containerkeyword, its value MUST be either
@list,
@set,
@language,
@index,
@id,
@graph,
@type, or be
null
or an array containing exactly any one of those keywords, or a
combination of @set and any of @index,
@id, @graph, @type,
@language in any order
.
@container may also be an array
containing @graph along with either @id or
@index and also optionally including @set.
If the value
is @language, when the term is used outside of the
@context, the associated value MUST be a language map.
If the value is @index, when the term is used outside of
the @context, the associated value MUST be an
index map.
TermsMUST NOT be used in a circular manner. That is,
the definition of a term cannot depend on the definition of another term if that other
term also depends on the first term.
The unaliased @container keyword MAY be used as a key in an expanded term definition.
Its value MUST be either
@list,
@set,
@language,
@index,
@id,
@graph,
@type, or be
null,
or an array containing exactly any one of those keywords, or a
combination of @set and any of @index,
@id, @graph, @type,
@language in any order.
The value may also be an array
containing @graph along with either @id or
@index and also optionally including @set.
@context
The @context keyword MUST NOT be aliased, and MAY be used as a key in the following objects:
The @language keyword MAY be aliased and MAY be used as a key in a value object.
Its value MUST be a string with the lexical form described in [BCP47] or be null.
The @list keyword MAY be aliased and MUST be used as a key in a list object.
The unaliased @listMAY be used as the value of the @container key within an expanded term definition.
Its value MUST be one of the following:
The unaliased @typeMAY be used as a key in an expanded term definition,
where its value may also be either @id or @vocab,
or as the value of the @container key within an expanded term definition.
Within a context, @type may be used as the key for an expanded term definition,
whose entries are limited to @container and @protected.
The @value keyword MAY be aliased and MUST be used as a key in a value object.
Its value key MUST be either a string, a number, true, false or null.
This keyword is described further in § 9.5 Value Objects.
JSON-LD is a
concrete RDF syntax
as described in [RDF11-CONCEPTS]. Hence, a JSON-LD document is both an
RDF document and a JSON document and correspondingly represents an
instance of an RDF data model. However, JSON-LD also extends the RDF data
model to optionally allow JSON-LD to serialize
generalized RDF Datasets.
The JSON-LD extensions to the RDF data model are:
In JSON-LD lists use native JSON syntax, either contained in a
list object, or described as such within a context. Consequently, developers
using the JSON representation can access list elements directly rather than
using the vocabulary for collections described in [RDF-SCHEMA].
RDF values are either typed literals
(typed values) or
language-tagged strings whereas
JSON-LD also supports JSON's native data types, i.e., number,
strings, and the boolean values true
and false. The JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API]
defines the conversion rules
between JSON's native data types and RDF's counterparts to allow round-tripping.
As an extension to the RDF data model,
literals without an explicit datatype
MAY include a base direction.
As there is currently no standardized mechanism for representing the base direction
of RDF literals, the JSON-LD to standard RDF transformation loses the base direction.
However, the Deserialize JSON-LD to RDF Algorithm
provides a means of representing base direction
using mechanisms which will preserve round-tripping through non-standard RDF.
Summarized, these differences mean that JSON-LD is capable of serializing any RDF
graph or dataset and most, but not all, JSON-LD documents can be directly
interpreted as RDF as described in RDF 1.1 Concepts [RDF11-CONCEPTS].
Authors are strongly encouraged to avoid labeling properties using blank node identifiers,
instead, consider one of the following mechanisms:
The normative algorithms for interpreting JSON-LD as RDF and serializing
RDF as JSON-LD are specified in the JSON-LD 1.1 Processing Algorithms and API
specification [JSON-LD11-API].
Publishers supporting both dataset and graph syntaxes have to ensure that
the primary data is stored in the default graph to enable consumers that do not support
datasets to process the information.
10.1 Serializing/Deserializing RDF
This section is non-normative.
The process of serializing RDF as JSON-LD and deserializing JSON-LD to RDF
depends on executing the algorithms defined in
RDF Serialization-Deserialization Algorithms
in the JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API].
It is beyond the scope of this document to detail these algorithms any further,
but a summary of the necessary operations is provided to illustrate the process.
The procedure to deserialize a JSON-LD document to RDF involves the
following steps:
Expand the JSON-LD document, removing any context; this ensures
that properties, types, and values are given their full representation
as IRIs and expanded values. Expansion
is discussed further in § 5.1 Expanded Document Form.
Deserializing this to RDF now is a straightforward process of turning
each node object into one or more triples. This can be
expressed in Turtle as follows:
Example 153: Turtle representation of expanded/flattened document
The process of serializing RDF as JSON-LD can be thought of as the
inverse of this last step, creating an expanded JSON-LD document closely
matching the triples from RDF, using a single node object
for all triples having a common subject, and a single property
for those triples also having a common predicate. The result may
then be framed by using the
Framing Algorithm
described in [JSON-LD11-FRAMING] to create the desired object embedding.
10.2 The rdf:JSON Datatype
RDF provides for JSON content as a possible literal value.
This allows markup in literal values.
Such content is indicated in a graph using a literal whose datatype is set to rdf:JSON.
The rdf:JSON datatype is defined as follows:
The IRI denoting this datatype
is http://www.w3.org/1999/02/22-rdf-syntax-ns#JSON.
Strings MUST be serialized with Unicode codepoints from U+0000 through U+001F
using lower case hexadecimal Unicode notation (\uhhhh) unless in the set
of predefined JSON control characters U+0008, U+0009,
U+000A, U+000C or U+000D
which SHOULD be serialized as \b, \t, \n, \f and \r respectively.
All other Unicode characters SHOULD be serialized "as is", other than
U+005C (\) and U+0022 (")
which SHOULD be serialized as \\ and \" respectively.
Issue
The JSON Canonicalization Scheme (JCS) [RFC8785]
is an emerging standard for JSON canonicalization.
This specification will likely be updated to require such a canonical representation.
Users are cautioned from depending on the
JSON literal lexical representation as an RDF literal,
as the specifics of serialization may change in a future revision of this document.
Despite being defined as a set of strings,
this value space is considered distinct from the value space of xsd:string,
in order to avoid side effects with existing specifications.
The lexical-to-value mapping
maps any element of the lexical space to the result of
Datatypes based on this namespace allow round-tripping of JSON-LD documents using base direction,
although the mechanism is not otherwise standardized.
The Deserialize JSON-LD to RDF Algorithm
can be used with the rdfDirection option
set to i18n-datatype to generate RDF literals using the i18n base to create an IRI
encoding the base direction along with optional language tag (normalized to lower case)
from value objects containing @direction by appending to https://www.w3.org/ns/i18n#
the value of @language, if any, followed by an underscore ("_") followed
by the value of @direction.
For improved interoperability, the language tag is normalized to
lower case when creating the datatype IRI.
The following example shows two statements with literal values of i18n:ar-EG_rtl,
which encodes the language tag ar-EG and the base direction rtl.
@prefix ex: <http://example.org/> .
@prefix i18n: <https://www.w3.org/ns/i18n#> .
# Note that this version preserves the base direction using a non-standard datatype.
[
ex:title "HTML و CSS: تصميم و إنشاء مواقع الويب"^^i18n:ar-eg_rtl;
ex:publisher "مكتبة"^^i18n:ar-eg_rtl
] .
10.4 The rdf:CompoundLiteral class and the rdf:language and rdf:direction properties
This section is non-normative.
This specification defines the rdf:CompoundLiteral class, which is in the domain
of rdf:language and rdf:direction to be used for describing RDF literal values
containing base direction and a possible language tag to be associated with the
string value of rdf:value on the same subject.
rdf:CompoundLiteral
A class representing a compound literal.
rdf:language
An RDF property.
The range of the property is an rdfs:Literal, whose value MUST be a well-formed [BCP47] language tag.
The domain of the property is rdf:CompoundLiteral.
rdf:direction
An RDF property.
The range of the property is an rdfs:Literal, whose value MUST be either "ltr" or "rtl".
The domain of the property is rdf:CompoundLiteral.
For improved interoperability, the language tag is normalized to
lower case when creating the datatype IRI.
The following example shows two statements with compound literals
representing strings with the language tagar-EG and base directionrtl.
@prefix ex: <http://example.org/> .
# Note that this version preserves the base direction using a bnode structure.
[
ex:title [
rdf:value "HTML و CSS: تصميم و إنشاء مواقع الويب",
rdf:language "ar-eg",
rdf:direction "rtl"
];
ex:publisher [
rdf:value "مكتبة",
rdf:language "ar-eg",
rdf:direction "rtl"
]
] .
Future versions of this specification
may incorporate subresource integrity [SRI] as a means of ensuring that cached and retrieved
content matches data retrieved from remote servers; see issue 86.
12. Privacy Considerations
The retrieval of external contexts can expose the operation of a JSON-LD processor,
allow intermediate nodes to fingerprint the client application through introspection of retrieved resources
(see [fingerprinting-guidance]),
and provide an opportunity for a man-in-the-middle attack.
To protect against this, publishers should consider caching remote contexts for future use,
or use the documentLoader
to maintain a local version of such contexts.
13. Internationalization Considerations
As JSON-LD uses the RDF data model, it is restricted by design in its ability to
properly record JSON-LD Values which are strings with left-to-right or right-to-left direction indicators.
Both JSON-LD and RDF provide a mechanism for specifying the language associated with
a string (language-tagged string), but do not provide a means of indicating
the base direction of the string.
Unicode provides a mechanism for signaling direction within a string
(see Unicode Bidirectional Algorithm [UAX9]),
however, when a string has an overall base direction which cannot be determined by the
beginning of the string, an external indicator is required,
such as the [HTML] dir attribute,
which currently has no counterpart for RDF literals.
The issue of properly representing base direction in RDF is not something that
this Working Group can handle, as it is a limitation or the core RDF data model.
This Working Group expects that a future RDF Working Group will consider the matter
and add the ability to specify the base direction of language-tagged strings.
Until a more comprehensive solution can be addressed in a future version of this
specification, publishers should consider this issue when representing strings
where the base direction of the string cannot otherwise be correctly inferred
based on the content of the string.
See [string-meta] for a discussion best practices for
identifying language and base direction for strings used on the Web.
The image consists of three dashed boxes, each describing a different
linked data graph. Each box consists of shapes linked with arrows describing
the linked data relationships.
The first box is titled "default graph: <no name>" describes two
resources: http://example.com/people/alice and http://example.com/people/bob
(denoting "Alice" and "Bob" respectively), which are
connected by an arrow labeled schema:knows which describes
the knows relationship between the two resources. Additionally, the "Alice" resource is related
to three different literals:
Alice
an RDF literal with no datatype or language.
weiblich | de
an language-tagged string with the value "weiblich" and language tag "de".
female | en
an language-tagged string with the value "female" and language tag "en".
The second and third boxes describe two named graphs, with the graph names
"http://example.com/graphs/1" and "http://example.com/graphs/1", respectively.
The second box consists of two resources:
http://example.com/people/alice and http://example.com/people/bob
related by the schema:parent relationship, and names the
http://example.com/people/bob "Bob".
The third box consists of two resources, one
named http://example.com/people/bob and the other unnamed.
The two resources related to each other using schema:sibling relationship
with the second named "Mary".
B. Relationship to Other Linked Data Formats
This section is non-normative.
The JSON-LD examples below demonstrate how JSON-LD can be used to
express semantic data marked up in other linked data formats such as Turtle,
RDFa, and Microdata. These sections are merely provided as
evidence that JSON-LD is very flexible in what it can express across different
Linked Data approaches.
B.1 Turtle
This section is non-normative.
The following are examples of transforming RDF expressed in [Turtle]
into JSON-LD.
B.1.1 Prefix definitions
The JSON-LD context has direct equivalents for the Turtle
@prefix declaration:
Example 154: A set of statements serialized in Turtle
In JSON-LD numbers and boolean values are native data types. While [Turtle]
has a shorthand syntax to express such values, RDF's abstract syntax requires
that numbers and boolean values are represented as typed literals. Thus,
to allow full round-tripping, the JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API]
defines conversion rules between JSON-LD's native data types and RDF's
counterparts. Numbers without fractions are
converted to xsd:integer-typed literals, numbers with fractions
to xsd:double-typed literals and the two boolean values
true and false to a xsd:boolean-typed
literal. All typed literals are in canonical lexical form.
Example 158: JSON-LD using native data types for numbers and boolean values
Note that this interpretation differs from [Turtle],
in which the literal 2.78 translates to an xsd:decimal.
The rationale is that most JSON tools parse numbers with fractions as
floating point numbers,
so xsd:double is the most appropriate datatype to render them back in RDF.
B.1.4 Lists
Both JSON-LD and [Turtle] can represent sequential lists of values.
The HTML Microdata [MICRODATA] example below expresses book information as
a Microdata Work item.
Example 164: HTML that describes a book using microdata
<dlitemscopeitemtype="http://purl.org/vocab/frbr/core#Work"itemid="http://purl.oreilly.com/works/45U8QJGZSQKDH8N"><dt>Title</dt><dd><citeitemprop="http://purl.org/dc/elements/1.1/title">Just a Geek</cite></dd><dt>By</dt><dd><spanitemprop="http://purl.org/dc/elements/1.1/creator">Wil Wheaton</span></dd><dt>Format</dt><dditemprop="http://purl.org/vocab/frbr/core#realization"itemscopeitemtype="http://purl.org/vocab/frbr/core#Expression"itemid="http://purl.oreilly.com/products/9780596007683.BOOK"><linkitemprop="http://purl.org/dc/elements/1.1/type"href="http://purl.oreilly.com/product-types/BOOK">
Print
</dd><dditemprop="http://purl.org/vocab/frbr/core#realization"itemscopeitemtype="http://purl.org/vocab/frbr/core#Expression"itemid="http://purl.oreilly.com/products/9780596802189.EBOOK"><linkitemprop="http://purl.org/dc/elements/1.1/type"href="http://purl.oreilly.com/product-types/EBOOK">
Ebook
</dd></dl>
Note that the JSON-LD representation of the Microdata information stays
true to the desires of the Microdata community to avoid contexts and
instead refer to items by their full IRI.
Example 165: Same book description in JSON-LD (avoiding contexts)
This section has been submitted to the Internet Engineering Steering
Group (IESG) for review, approval, and registration with IANA.
application/ld+json
Type name:
application
Subtype name:
ld+json
Required parameters:
N/A
Optional parameters:
profile
A non-empty list of space-separated URIs identifying specific
constraints or conventions that apply to a JSON-LD document according to [RFC6906].
A profile does not change the semantics of the resource representation
when processed without profile knowledge, so that clients both with
and without knowledge of a profiled resource can safely use the same
representation. The profile parameter MAY be used by
clients to express their preferences in the content negotiation process.
If the profile parameter is given, a server SHOULD return a document that
honors the profiles in the list which it recognizes,
and MUST ignore the profiles in the list which it does not recognize.
It is RECOMMENDED that profile URIs are dereferenceable and provide
useful documentation at that URI. For more information and background
please refer to [RFC6906].
This specification defines six values for the profile parameter.
All other URIs starting with http://www.w3.org/ns/json-ld
are reserved for future use by JSON-LD specifications.
Other specifications may publish additional profile parameter
URIs with their own defined semantics.
This includes the ability to associate a file extension with a profile parameter.
When used as a media type parameter [RFC4288]
in an HTTP Accept header [RFC7231],
the value of the profile parameter MUST be enclosed in quotes (") if it contains
special characters such as whitespace, which is required when multiple profile URIs are combined.
When processing the "profile" media type parameter, it is important to
note that its value contains one or more URIs and not IRIs. In some cases
it might therefore be necessary to convert between IRIs and URIs as specified in
section 3 Relationship between IRIs and URIs
of [RFC3987].
Since JSON-LD is intended to be a pure data exchange format for
directed graphs, the serialization SHOULD NOT be passed through a
code execution mechanism such as JavaScript's eval()
function to be parsed. An (invalid) document may contain code that,
when executed, could lead to unexpected side effects compromising
the security of a system.
When processing JSON-LD documents, links to remote contexts and frames are
typically followed automatically, resulting in the transfer of files
without the explicit request of the user for each one. If remote
contexts are served by third parties, it may allow them to gather
usage patterns or similar information leading to privacy concerns.
Specific implementations, such as the API defined in the
JSON-LD 1.1 Processing Algorithms and API specification [JSON-LD11-API],
may provide fine-grained mechanisms to control this behavior.
JSON-LD contexts that are loaded from the Web over non-secure connections,
such as HTTP, run the risk of being altered by an attacker such that
they may modify the JSON-LD active context in a way that
could compromise security. It is advised that any application that
depends on a remote context for mission critical purposes vet and
cache the remote context before allowing the system to use it.
Given that JSON-LD allows the substitution of long IRIs with short terms,
JSON-LD documents may expand considerably when processed and, in the worst case,
the resulting data might consume all of the recipient's resources. Applications
should treat any data with due skepticism.
As JSON-LD places no limits on the IRI schemes that may be used,
and vocabulary-relative IRIs use string concatenation rather than
IRI resolution, it is possible to construct IRIs that may be
used maliciously, if dereferenced.
Interoperability considerations:
Not Applicable
Published specification:
http://www.w3.org/TR/json-ld
Applications that use this media type:
Any programming environment that requires the exchange of
directed graphs. Implementations of JSON-LD have been created for
JavaScript, Python, Ruby, PHP, and C++.
Additional information:
Magic number(s):
Not Applicable
File extension(s):
.jsonld
Macintosh file type code(s):
TEXT
Person & email address to contact for further information:
Ivan Herman <ivan@w3.org>
Intended usage:
Common
Restrictions on usage:
N/A
Author(s):
Manu Sporny, Dave Longley, Gregg Kellogg, Markus Lanthaler, Niklas Lindström
Requests the server to return the requested resource as JSON-LD
in compacted document form.
As no explicit context resource is specified, the server compacts
using an application-specific default context.
Example 168: HTTP Request with profile requesting a compacted document with a reference to a compaction context
Requests the server to return the requested resource as JSON-LD
in both compacted document form
and flattened document form.
Note that as whitespace is used to separate the two URIs, they
are enclosed in double quotes (").
D. Open Issues
This section is non-normative.
The following is a list of issues open at the time of publication.
An expanded term definition can now have an
@nest property, which identifies a term expanding to
@nest which is used for containing properties using the same
@nest mapping. When expanding, the values of a property
expanding to @nest are treated as if they were contained
within the enclosing node object directly.
The JSON syntax has been abstracted into an internal representation
to allow for other serializations that are functionally equivalent
to JSON.
The value for @container in an expanded term definition
can also be an array containing any appropriate container
keyword along with @set (other than @list).
This allows a way to ensure that such property values will always
be expressed in array form.
In JSON-LD 1.1, terms will be chosen as compact IRI prefixes
when compacting only if
a simple term definition is used where the value ends with a URI gen-delim character,
or if their expanded term definition contains
a @prefixentry with the value true. The 1.0 algorithm has
been updated to only consider terms that map to a value that ends with a URI
gen-delim character.
Values of properties where the associated term definition
has @container set to @graph are interpreted as
implicitly named graphs, where the associated graph name is
assigned from a new blank node identifier. Other combinations
include ["@container", "@id"], ["@container", "@index"] each also
may include "@set", which create maps from the
graph identifier or index value similar to index maps
and id maps.
F. Changes since JSON-LD Community Group Final Report
This section is non-normative.
Lists may now have items which are themselves lists.
Values of @type, or an alias of @type, may now have their @container set to @set
to ensure that @typeentries are always represented as an array. This
also allows a term to be defined for @type, where the value MUST be a map
with @container set to @set.
The vocabulary mapping can be a relative IRI reference, which is evaluated
either against an existing default vocabulary, or against the document base.
This allows vocabulary-relative IRIs, such as the
keys of node objects, are expanded or compacted relative
to the document base.
(See Security Considerations in § C. IANA Considerations
for a discussion on how string vocabulary-relative IRI resolution via concatenation.
)
Added support for "@type": "@none" in a term definition to prevent value compaction.
Define the rdf:JSON datatype.
A context may contain an @importentry used to reference a remote context
within a context, allowing JSON-LD 1.1 features to be added to contexts originally
authored for JSON-LD 1.0.
A node object may include an included block,
which is used to contain a set of node objects which are treated
exactly as if they were node objects defined in an array including the containing
node object.
This allows the use of the object form of a JSON-LD document when there is more
than one node object being defined, and where those node objects
are not embedded as values of the containing node object.
The alternate link relation can be used to supply an alternate location for
retrieving a JSON-LD document when the returned document is not JSON.
Changed normative definition of the rdf:JSON datatype in § 10.2 The rdf:JSON Datatype
to describe a normative canonicalization.
This is in response to Issue 323.
The editors would like to specially thank the following individuals for making significant
contributions to the authoring and editing of this specification:
Timothy Cole (University of Illinois at Urbana-Champaign)
Gregory Todd Williams (J. Paul Getty Trust)
Ivan Herman (W3C Staff)
Jeff Mixter (OCLC (Online Computer Library Center, Inc.))
David Lehn (Digital Bazaar)
David Newbury (J. Paul Getty Trust)
Robert Sanderson (J. Paul Getty Trust, chair)
Harold Solbrig (Johns Hopkins Institute for Clinical and Translational Research)
Simon Steyskal (WU (Wirschaftsuniversität Wien) - Vienna University of Economics and Business)
A Soroka (Apache Software Foundation)
Ruben Taelman (Imec vzw)
Benjamin Young (Wiley, chair)
Additionally, the following people were members of the Working Group at the time of publication:
Steve Blackmon (Apache Software Foundation)
Dan Brickley (Google, Inc.)
Newton Calegari (NIC.br - Brazilian Network Information Center)
Victor Charpenay (Siemens AG)
Sebastian Käbisch (Siemens AG)
Axel Polleres (WU (Wirschaftsuniversität Wien) - Vienna University of Economics and Business)
Leonard Rosenthol (Adobe)
Jean-Yves ROSSI (CANTON CONSULTING)
Antoine Roulin (CANTON CONSULTING)
Manu Sporny (Digital Bazaar)
Clément Warnier de Wailly (CANTON CONSULTING)
A large amount of thanks goes out to the JSON-LD Community Group participants who worked through many of the technical issues on the mailing list and the weekly telecons: Chris Webber, David Wood, Drummond Reed, Eleanor Joslin, Fabien Gandon, Herm Fisher, Jamie Pitts, Kim Hamilton Duffy, Niklas Lindström, Paolo Ciccarese, Paul Frazze, Paul Warren, Reto Gmür, Rob Trainer, Ted Thibodeau Jr., and Victor Charpenay.