Wikipedia talk:WikiProject Categories

See also: WT:CAT and WT:CFD

"Template:R from deadname" listed at Redirects for discussion

The redirect Template:R from deadname has been listed at redirects for discussion to determine whether its use and function meets the redirect guidelines. Readers of this page are welcome to comment on this redirect at Wikipedia:Redirects for discussion/Log/2023 August 30 § Template:R from deadname until a consensus is reached.

I’m notifying WP:CATP as one of the options is to turn Template:R from deadname into its own rcat, which would then result in the creation of Category:Redirects from deadnames or similar. Best, A smart kitten (talk) 17:45, 1 September 2023 (UTC)

"We Didn't Start the Fire" Category

I was thinking about creating a category for events mentioned in the song "We Didn't Start the Fire," but I can definitely see how that could be considered trivial. Certainly the election of Harry Truman is not most notable for its inclusion in a Billy Joel song, but there are song events that are arguably best remembered for their inclusion in the song (Syringe Tide comes to mind). I feel that this could be a useful category, but would like others' input. Remainsuncertain (talk) 21:30, 23 September 2023 (UTC)

Remainsuncertain Ask Koavf. I have seen them have some interest in such niche cats. Regards, --Thinker78 (talk) 03:08, 1 October 2023 (UTC)

Redundant cat

This categories seem to mirror each other. Category:Crime by century and Category:Crimes by century. Thoughts? Regards,--Thinker78 (talk) 03:11, 1 October 2023 (UTC)

The Crimes ones should be about particular events which were of a criminal nature, such as the Hatton Garden job. The Crime ones should be about more general topics, such as changes to the law and the events that precipitated the change. --Redrose64 🌹 (talk) 07:13, 1 October 2023 (UTC)

I think it is rather confusing such arrangement. Regards, Thinker78 (talk) 19:21, 1 October 2023 (UTC)

Wikipedia categories named after musical groups

Enforcement of WP:OCEPON seems to be particularly focused on eponymous categories for bands (at least when compared to other topics like political parties). I created Category:Greta Van Fleet earlier this year and it was deleted on this basis so I was wondering how big does a category have to be for it to be considered worthy? Charles Essie (talk) 20:21, 2 October 2023 (UTC)

Any way to know number of entries of deleted categories

I was wondering if there is a way to know how many entries a deleted category had at any given time. Specifically in this case, Category:Assassinated American former and incumbent party officials. Regards, --Thinker78 (talk) 21:45, 12 October 2023 (UTC)

First, you would need to obtain a database dump from the time that is of interest. This is more a WP:VPT thing, not a WikiProject matter. --Redrose64 🌹 (talk) 23:09, 13 October 2023 (UTC)

Petscan question

I ran a Petscan query including Category:Homicide and Category:Politicians but for some reason, Zeus showed up, no idea why. Anyone knows why and how to find out? Regards, Thinker78 (talk) 01:04, 30 October 2023 (UTC)

a) Homicide > Infanticide > Child sacrifice > Cronus > Children of Cronus

b) Politicians > Heads of state > Monarchs > Monarchs in Greek mythology > Kings in Greek mythology

Both categories have actually more paths to Zeus than those. I had the same question not long ago (but can't remember where), and I was given the code for a query at quarry:, and I used that to retrieve the above results. -- Michael Bednarek (talk) 02:33, 30 October 2023 (UTC)

Incredibly useful answer, I appreciate it! Best regards, Thinker78 (talk) 03:56, 30 October 2023 (UTC)

Discussion at Wikipedia:Categorization

 You are invited to join the discussion at Wikipedia talk:Categorization#Caste-related category questions, which is within the scope of this WikiProject. Beccaynr (talk) 14:49, 30 October 2023 (UTC)

Archive categorization

Hello! What's the best way to remove the Cuisine by country category from this archive page: Talk:Cuisine of Luxembourg/Archive 1? It was linked by someone in a discussion thread and I don't want to modify any of the content since archive content generally should not be edited. BaduFerreira (talk) 13:37, 1 November 2023 (UTC)

It's perfectly legitimate to correct such mistakes. -- Michael Bednarek (talk) 13:43, 1 November 2023 (UTC)

Cool, I just copyedited it away. Thank you! BaduFerreira (talk) 13:47, 1 November 2023 (UTC)

@BaduFerreira For future reference: When a category is being mentioned, rather than assigned to a page, it needs a ":" before the word "Category". That's what was missing and has now been fixed. PamD 13:56, 1 November 2023 (UTC)

Oh okay, I was looking for a way to preserve the linked category without removing it outright but I misinterpreted Michael's comment as to just remove it entirely. Thank you for the heads-up! BaduFerreira (talk) 14:01, 1 November 2023 (UTC)

Request for comment SmallCat

There is a discussion that may be of your interest about a Request for comment on replacement to SmallCat guideline. Regards, Thinker78 (talk) 05:47, 24 November 2023 (UTC)

@Marcocapelle, Nederlandse Leeuw, RevelationDirect, and Jc37: Courtesy ping to editors working on the Wikipedia:Merge for now essay and author of a previous RfC that deprecated SmallCat and which I analyzed to make the proposal. Regards, Thinker78 (talk) 05:54, 24 November 2023 (UTC)

Idea for category or list

A category or list of "Bills left unsigned by US President that became law" would be useful for research.

I am thinking it might be more appropriate as a list but I could use some guidance.

I could not find an existing similar category or list. Mike Richardson (talk) 05:49, 29 November 2023 (UTC)

Discussion at Wikipedia:Categories for discussion/Log/2023 December 4 § Category:Fair use images

 You are invited to join the discussion at Wikipedia:Categories for discussion/Log/2023 December 4 § Category:Fair use images. -- Marchjuly (talk) 05:15, 4 December 2023 (UTC)

Alternatives to PetScan?

There seems to be issues with PetScan. Are there alternatives to it? Regards, Thinker78 (talk) 05:07, 19 December 2023 (UTC)

Glad to know I wasn’t the only one having issues with it. I thought I must have been using it incorrectly! Best, ‍—‍a smart kitten_[meow] 09:29, 19 December 2023 (UTC)

Cirrus search, despite its limitations, has more features than many editors realise. AWB can also produce lists, even if the user has no intention of editing those pages with AWB. For editors familiar with SQL, there are Quarry and {{Database report}}, though both take far longer to code than PetScan. Of course, we have WhatLinksHere. Certes (talk) 10:28, 19 December 2023 (UTC)

I'm constantly getting the good old ®exp_filter bug (i.e. if PetScan fails, check all the tabs and fields for "®exp_filter") that's still not fixed. 85.76.13.79 (talk) 12:19, 19 December 2023 (UTC)

That bug occurs when one copies the "Link to a pre-filled form...", pastes it into a wikitext or HTML page then views that in a browser (details). Certes (talk) 13:51, 19 December 2023 (UTC)

Yes, but it also sometimes happens in other scenarios, too, e.g.:

• 1) I opened https://petscan.wmflabs.org/ (so not a pre-filled url)
• 2) Only filled the fields:

• a) Categories
• b) Depth
• c) Has none of these templates

• 3) Clicked "Do it"
• 4) Search failed and I found the "®exp_filter" in the "Links to" field

85.76.13.79 (talk) 14:03, 19 December 2023 (UTC)

That is surprising. I've not seen that behaviour before, and it doesn't fit the explanation I gave in the details link above. Perhaps there are multiple related bugs. Certes (talk) 14:27, 19 December 2023 (UTC)

Since it's happening to me all the time now, I managed to make a quick video to prove that it happens: https://streamable.com/eltfm4 (link expires in 2 days). 85.76.13.79 (talk) 14:31, 19 December 2023 (UTC)

I'd suggest reposting these details over at Wikipedia talk:PetScan, and then pinging or user talk messaging its maintainer, User:Magnus Manske. He edited a month ago and is still an admin, so may still be around. –Novem Linguae (talk) 03:46, 21 December 2023 (UTC)

Petscan acting out again

Tracked in github.com
Issue #155

Now the situation of Petscan is worse. Can't even access the tool and there is instead some message, "Wikimedia Cloud Services Error. This web service cannot be reached. Please contact a maintainer of this project." Regards, Thinker78 (talk) 18:29, 26 January 2024 (UTC)

Possible template to expand underfilled categories.

{{Import from list}}. Sometimes, a list article has more bluelinked entries than a corresponding category. The idea is that this template would be placed on the category page. Thoughts? Mach61 (talk) 02:22, 23 December 2023 (UTC)

You sort of didn't explain the use of the template. Regards, Thinker78 (talk) 18:30, 26 January 2024 (UTC)

Circular categories

Category:Fictional doves and pigeons is inside Category:Fictional Columbidae, which is inside Category:Fictional doves and pigeons. Given that "doves and pigeons" is the exact same thing as Columbidae, what should we do? Kk.urban (talk) 03:01, 5 January 2024 (UTC)

You can submit them for merger at Wikipedia:Categories for discussion. Place Clichy (talk) 03:22, 5 January 2024 (UTC)

There are several other loops where A is a subcategory of B and B is a subcategory of A. I've listed them in User:Certes/Reports/Circular categories. In many cases, A and B are identical: for example, Category:1939 in gymnastics is a subcategory of itself. Can I assume that these are mistakes and remove them from themselves (except for esoteric metadata such as Category:Hidden categories which, being a hidden category, is correctly a member of itself)? Certes (talk) 23:36, 6 January 2024 (UTC)

Cats that are subcats of themselves are reported at Wikipedia:Database reports/Self-categorized categories, something that has only recently been updated after a fifteen-month hiatus. At one period, it was run weekly. The way to deal with these is indeed to remove the category from itself, but that's not the only action - you must also ensure that it has at least one appropriate parent category (example). There are a few categories which are intentionally members of themselves - two of these are by design: Category:Hidden categories and Category:Noindexed pages; there is also Category:Template Large category TOC via CatAutoTOC on category with 2,001–5,000 pages, as a side-effect of using {{CatAutoTOC}}.

Apart from those three, there are two main reasons that a category might be inside itself - one is that the person creating the cat page didn't understand the categorisation system (as with Category:Synchronized sound films), the other is because of a category merge (example). Regarding the latter, I have pointed this problem out before, see Wikipedia talk:Categories for discussion/Working/Archive 2#Incorrect cat changes and Wikipedia talk:Categories for discussion/Archive 17#Bad edits by Cydebot. --Redrose64 🌹 (talk) 15:28, 7 January 2024 (UTC)

Thanks for the reply. I just stumbled across Wikipedia:Database reports/Self-categorized categories, as you kindly linked it in an edit summary which I found when trying to fix something you'd already fixed. I'd spotted two of the three deliberate self-categorisations and will make a note of Noindexed so I don't try to "mend" it. I've applied a few different solutions such as finding better parents or nominating the category for deletion, but will leave it to the experts in future now I know that someone with a clue is on the case. Certes (talk) 20:35, 7 January 2024 (UTC)

One for the experts is Category:Colleges affiliated to Bihar Engineering University. It consists of a template, which displays a huge navbox listing colleges that aren't in the category and categorises the category as its own single parent and only child. Certes (talk) 20:40, 7 January 2024 (UTC)

That one's easy, see these edits. I only added the cat to two articles because those were the only ones transcluding the navbox that weren't categorised properly. --Redrose64 🌹 (talk) 22:50, 7 January 2024 (UTC)

Returning to my first tangent, User:Certes/Reports/Circular categories now excludes categories which include themselves. In other words, it only lists loops of length exactly two, though loops of other lengths may also require attention. Certes (talk) 20:53, 7 January 2024 (UTC)

I've started working slowly through circular category pairs. Does this sample of edits look helpful, or should I leave it to the experts? Certes (talk) 22:25, 7 January 2024 (UTC)

We also have User:SDZeroBot/Category cycles, which includes loops of any length. And your edits look good to me. * Pppery * _{it has begun...} 18:08, 8 January 2024 (UTC)

Thanks. Some are clear-cut: A is a subset of B but not vice versa. However, most cases have a Venn diagram with two significant crescents. For example, Animals of Foo and Wildlife of Foo are similar but only the first includes livestock and only the second includes flora. These I have left alone, as neither category link is obviously better than the other, though there is a case for removing both. Certes (talk) 18:53, 8 January 2024 (UTC)

They both should be subcats of Fauna of Foo. --Redrose64 🌹 (talk) 21:19, 8 January 2024 (UTC)

Really? I'd have thought that Animals was almost synonymous with (and hence redundant to) Fauna. Wildlife refers to undomesticated animal species, but has come to include all organisms that grow or live wild in an area, so it could be interpreted as another synonym for Fauna or as a wider class including flora etc. which sounds like a parent category rather than a subcat. Perhaps the problem is that many categories lack precise definitions (or that I'm too thick to find them). Certes (talk) 22:04, 8 January 2024 (UTC)

Sorry, I meant Biota of Foo. --Redrose64 🌹 (talk) 22:31, 8 January 2024 (UTC)

Message here BinaryBrainBug (talk) 20:37, 20 January 2024 (UTC)

List of all articles of a category and its subcategories?

Dear Categoryographers,

I know how to use Special:CategoryTree to find the tree of subcategories of a given category. But suppose I just wanted the list of articles that belong to a category or its subcategories? For a high-level category like Category:Mathematics, it's totally infeasible to construct this by hand from the tree; is there a better way?

Thanks, JBL (talk) 19:28, 12 January 2024 (UTC)

It sounds like a job for WP:PETSCAN, but that service seems down at the moment. DMacks (talk) 19:35, 12 January 2024 (UTC)

Thanks for the quick response. It does seem to be down, but I'll check it again later. FWIW someone else has suggested to me that https://pageviews.wmcloud.org/massviews/ can also be used for this purpose. --JBL (talk) 19:49, 12 January 2024 (UTC)

It is not down, it is unstable—one moment up, next time down, five minutes later up. Regards, Thinker78 (talk) 21:03, 12 January 2024 (UTC)

Beware that some things that look like subcategories aren't. Most Many unexpected categories are subcats of Mathematics by some devious route. Certes (talk) 19:53, 12 January 2024 (UTC)

Certes, as a person who does not think about categories at all (well, maybe on those occasions when I draft a new article), I'm afraid your comment is a bit obscure -- can you spell your meaning out more for me? (If the wmcloud massviews calculation can be believed (I'm not 100% sure), there are roughly 16,000 articles in Cat:Math and its subcats, so it couldn't really be true that most categories belonged in the Cat:Math tree in that case, right?) --JBL (talk) 19:57, 12 January 2024 (UTC)

Examples:

• Voyagers! is in Cultural depictions of Albert Einstein is in Cultural depictions of mathematicians is in Mathematicians is in Mathematics
• Richmond Park is in Bertrand Russell is in 19th-century English mathematicians is in English mathematicians by century is in English mathematicians is in British mathematicians is in Mathematics in the United Kingdom‎ is in Mathematics by country‎ is in Mathematics‎
• Humpty Dumpty is in Category:Lewis Carroll characters is in Category:Lewis Carroll is in Category:19th-century English mathematicians (then as above)

Those articles might not be ones you would expect to find under Mathematics. Certes (talk) 21:41, 13 January 2024 (UTC)

@Certes@JayBeeEll Rather than Most categories are subcats of Mathematics by some devious route., I think what is shown here is that "Most articles are in subcats of Mathematics by some devious route." Not quite the same. PamD 22:02, 13 January 2024 (UTC)

I started finding example surprising subcategories but then noticed that the original query was about articles. "Most" may be an exaggeration, but there are certainly surprising subcats. Some category examples:

• Mathematics > Mathematical constants > 1 (number) > Solo activities > Individual sports‎ > Category:Boxing
• Mathematics > Fields of mathematics > Applied mathematics > Cryptography > Security engineering > Category:Prisons
• Mathematics > Fields of mathematics > Dynamical systems > Electrodynamics > Light > Category:Vision
• Mathematics > Fields of mathematics > Elementary mathematics > Integers > 2 (number) > Duos > Category:Fictional duos
• Mathematics > Statistical concepts > Statistical regions > Statistical regions of Serbia > Vojvodina > Languages of Vojvodina > Category:Serbian language

These aren't isolated examples; I think a lot of the category tree can be traced back to Mathematics by at least one route where the individual steps are plausible even if the overall effect can be confusing. Certes (talk) 22:40, 13 January 2024 (UTC)

Not isolated at all. quarry:query/75121 shows why the article Electrothermal-chemical technology is in the category tree Category:Opera. -- Michael Bednarek (talk) 01:36, 14 January 2024 (UTC)

Ok interesting, thanks. This seems like pretty compelling evidence that the 16,000 or so articles found by https://pageviews.wmcloud.org/massviews/ are only a small fraction of the total; maybe it has a cutoff for how deep in the tree it looks (though it seems, based on Certes' examples, that even five levels deep is enough to find some stuff pretty distant from the core topic area). --JBL (talk) 17:11, 14 January 2024 (UTC)

Somehow related

What we desperately need is a flag to say which categories record a strict is-a relationship and which, although still valuable, record an "is somehow related to" relationship. Then we can have trees limited to is-a links. However, I'm too lazy to spend the rest of my life adding those flags, so I can't really expect anyone else to volunteer either. Certes (talk) 17:56, 14 January 2024 (UTC)

I would do it for the articles that I work on if it would work reliably, and probably for some others too, but it would indeed be an immense task. · · · Peter Southwood ^(talk): 18:02, 21 January 2024 (UTC)

The vagueness of relatedness is a serious shortcoming of the category method. Wikidata handles such questions by separate properties such as "Instance of", "Part of", "Subset of", "Located in", "Author of", "Parent of", "Influenced by", "Employed by", and so forth. I figure supplementing the cat system with a lot of template flags would take forever and a day, whilst cooking up an easier way to look at the tree through WD might take only half the time. Jim.henderson (talk) 02:20, 16 January 2024 (UTC)

I do not follow WD development closely, but is there a way to do the equivalent of looking a the category listing? On enwiki, we can walk up and down the tree, but last I knew of WD we could walk up from an article ("A is-a B") but not back down ("what else is-a B?"). DMacks (talk) 02:23, 16 January 2024 (UTC)

The Wikidata Query Service can answer that sort of question but you'd need to write a SPARQL query. Certes (talk) 11:29, 16 January 2024 (UTC)

@DMacks: A utility to show the Wikidata relationship tree in graphical form was written by Pintoch (talk · contribs), I don't recall how it's accessed. --Redrose64 🌹 (talk) 12:17, 16 January 2024 (UTC)

@Redrose64: hi! I don't remember writing such a tool myself, but I can point you to a few which do that:

• the Wikidata Graph Builder is a very versatile tool to visualize the class hierarchy (see for instance their example about physicists.
• the Wikidata ontology explorer, which you can feed the Qid of a class you want to explore (such as sports league (Q623109)).
• the tool it is based on, Wikidata generic tree, which might be a bit less convenient to use because you need to figure out how to tweak the URL for it to do what you need

− Pintoch (talk) 10:21, 29 January 2024 (UTC)

I have taken the liberty of separating the last few replies into a new section. The big disadvantage of Wikidata SPARQL queries is that they are command lines. If we don't stay in touch with the ancient command traditions of Unix, DOS, and the like, we quickly forget how to do it. A year or two ago, WD had an "Entity Graph" feature. Click on the three dots to the right of the Q number. This created and ran a query to show every directly related WD item, and the Property that relates them, and some of the secondary (related to related) items if there was space enough in the window. The past few months, it has not worked; it always comes back as "Query is malformed". Seems to me the Entity Graph would be a useful feature, but it has been broken a long time. Perhaps a wide gulf has opened up, between WD and WP editors. Jim.henderson (talk) 05:00, 28 January 2024 (UTC)