This is an archived snapshot of W3C's public bugzilla bug tracker, decommissioned in April 2019. Please see the home page for more details.
The source document books2.xml is invalid against its schema books2.xsd. The schema defines an ID child element CATEGORY/CAT but the instance has a child element CATEGORY/CODE
Sigh. I was validating the source documents, but without turning schema validation on. The schema should be changed to allow CATEGORY/CODE instead of CATEGORY/CAT. As I see that this has just been done, I'll close this bug.