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RE: Simple xpath software request

• To: <xml-dev@l...>
• Subject: RE: Simple xpath software request
• From: Elliotte Rusty Harold <elharo@m...>
• Date: Sun, 3 Mar 2002 10:44:23 -0500
• In-reply-to: <005a01c1c1d3$08d8a300$66816bd5@pcukmka>
• References: <005a01c1c1d3$08d8a300$66816bd5@pcukmka>

At 10:14 AM +0000 3/2/02, Michael Kay wrote:

>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.
-- 

+-----------------------+------------------------+-------------------+
| Elliotte Rusty Harold | elharo@m... | Writer/Programmer |
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|          The XML Bible, 2nd Edition (Hungry Minds, 2001)           |
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