NM-XQ-6: xs:anyUri and xs:string

Build-in type xs:anyUri deserves better treatment in my opinion.

Currently it can be only compared with another xs:anyUri or casted to string.
But basically it is a string with additional restriction on structure (like pattern facet).
So xs:anyUri should be treated as derivation by restriction from xs:string by all XPath/XQuery rules.
This will allow to define function signatures using xs:anyUri and remove lexical checks from definitions
of functions.
Maybe it will be possible to change derivation diagram in XML Schema 1.1 and reference it instead
of 1.0 in XPath 2.0 / XQuery 1.0 ? This will be simpliest solution.
(and btw allow placing dayTimeDuration and yearMonthDuration in schema namespace)

Best Regards,
Noe Michejda
7th Portal S.C.