Re: TREX TC minutes from 2001-04-19

[Kohsuke KAWAGUCHI <kohsuke.kawaguchi@eng.sun.com>]

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                   kohsuke.kawaguchi@eng.sun.com