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- To: xml-dev@lists.xml.org
- Subject: Re: XPath and XSD/RNG
- From: "Robert C. Lyons" <boblyons@unidex.com>
- Date: Wed, 01 Jun 2005 20:23:04 -0400
- Cc: stefan.tilkov@innoq.com
- In-reply-to: <1117657238.3338.ezmlm@lists.xml.org>
- References: <1117657238.3338.ezmlm@lists.xml.org>
- User-agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.2) Gecko/20040803
Stefan Tilkov wrote:
"Is there a way to check whether an XPath expression could possibly be
true for a document conforming to a particular W3C XML Schema (or
Relax NG schema) without having access to the document? Is this
something that toolkits support?
E.g. if the schema disallows /root/element/subelement, the XPath
expression /root/element/subelement[0] cannot yield a non-null result
for any conforming document."
Stefan,
It's not possible to write a general algorithm that determines
whether or not an XPath expression could possibly be true
for all documents that conform to a schema. This problem is
undecidable. Also, the problem of whether or not an XPath
expression is satisfiable is undecidable.
For more details, please see:
http://www.idealliance.org/papers/extreme03/html/2003/Lyons01/EML2003Lyons01.html
Best regards,
Bob Lyons
XML and Java Consultant
www.unidex.com
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