status of "collections" in XPath / XQuery

["Brian Vickery" <macacos@linkline.com>]

What is the status of defining "collections" in XPath or XQuery?  The use cases specified by W3C seem to be more

at the "collection" level than specific documents.  It seems that each book in a bibliographies document is better

modeled as a document in a collection called "bibliographies".

 

Is there thought going on regarding constraints on collections (when they are defined)?  I may want to have all

invoice numbers in a collection be unique.