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> >Nothing in a schema can make an XPath 1.0 expression invalid. What is > >possible is that by examination of a schema you can > statically determine > >that a particular XPath expression will return an empty node-set. > > That seems to me a very dangerous thing to do. While you could > determine that this is true for *valid* documents, not all documents > are valid, not even all documents that reference a schema. XPath > (both 1.0 and 2.0) does not require validity. A conformant XPath > processor should not fail when faced with an invalid but well-formed > document. > > I suppose it would be possible to first test validity, and then, once > the document had been validated, use these optimizations. However, > I'm not sure that this would actually buy you anything in the long > run. It will probably be possible in XSLT 2.0 to state that a stylesheet is designed to work only with source documents that are valid against a particular schema. This will enable the stylesheet to be optimized to process such documents, and to reject documents that are not valid against that schema. Obviously this will be optional; it will still be possible to write generic stylesheets to process any well-formed document. Michael Kay Software AG home: Michael.H.Kay@n... work: Michael.Kay@s...
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