As James said, XML Schema now has very simple subset of XPath, which is
quite similar to the UCM. The only significant difference I saw is that
XML Schema allows XPaths to start with ".//", whereas UCM don't.
Several bad news wrt UCM:
* it assumes the grammar is unambiguous.
I felt that they are merely assuming the instance is unambiguous. So
maybe we can avoid this by making ambiguous instances invalid when
enforcing key/keyref constraint.
* we cannot enforce consistency.
They proved that checking consistency of key/keyref constraints is
undecidable or NP-hard in some subsets. So we can't reject some
of the malformed grammars.
--
Kohsuke KAWAGUCHI +1 650 786 0721
Sun Microsystems
