Armed with a recent Xerces, I was able to diagnose and resolve the ambiguity problems present in the previous release. At least, I was able to satisfy Xerces which has a reputation for being quite picky. The ambiguity about ambiguity still exists in the spec, so this could be wrong as well.
Remarkably, the changes necessary to remove ambiguity were not that onerous.
In DocBook, the
db:linkgroup has been removed from
db:linkis also a member of
db:ubiq.inlines, it was causing a UPA violation. This change shouldn't have any impact on the set of documents that are considered valid.
In the XSD 1.0 version of Publishers, the Dublin Core elements have been removed from the
infoelement. They cause a UPA conflict with the
xs:anythat is (supposed) to allow metadata from other namespaces. The process contents setting for “any” has been changed from “skip” to “lax” so that Dublin Core elements (if present) will still be validated against their schema types. I think.
I didn't change the XSD 1.1 schema because (again, I think) the rules for UPA have been softened in this case in XSD 1.1
As a result, I think I now have XML Schemas for DocBook and Publishers. If your favorite tool balks on one of these, please let me know. Likewise, if you encounter documents that you think are valid DocBook V5.0 documents that these schemas reject, please let me know.
For the sake of completeness, I'd also be interested in documents that are not valid DocBook V5.0 documents but that these schemas accept. Note, however, that these schemas are not normative and they will not detect some valididity problems. So such documents aren't necessarily a bug.