We describe a software framework, GAIA, that supports semi-automated annotation of uncharacterized sequence data. The annotation framework incorporates annotation by data source integration, data analysis, and manual data entry. Components of the system include a configurable, open data analysis pipeline, a relational information storage manager, and Java-based graphical user interfaces. We discuss design decisions and tradeoffs in building such a system, and policies and strategies for producing consistent, uniform, high quality annotation.