size of XQuery developer community

[Ken North]

>> schema evolution was one of the common use cases (the others being managing/querying documents, certain types of data integration, and semi-structured data).

PODS at the UCLA Health System fits the common use case you describe. It is part of a service-oriented architecture and it exposes service interfaces for users of clinical systems.

PODS handles a steady stream of new forms and XML schemas (currently more than 400) and supports HL7-compliant  messaging. The database grows by about 12,000 new documents per day, with patient metadata stored as XML in a DB2 database that's currently about 30 million rows.