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Re: [xml-dev] Be careful writing XPath expressions when the XML couldhave non-existent elements

Did not read the article but stating the obvious  from a strictly pattern matching XSLT perspective if there is no element then there is no pattern to match. 

If you  like to save your brain from the burden of all the edge cases - don't go there.

On Tue, Jul 29, 2014 at 10:43 AM, Costello, Roger L. <costello@mitre.org> wrote:
Hi Folks,

Are you writing XPath expressions?

XPath is embedded in a lot of things: XQuery, Schematron, XSLT, XML Schema. If you are using XML, there is a good chance you are writing XPath expressions.

Heads up!

Failure to take into account the following rule will result in countless headaches and hard-to-detect bugs.

        Rule: The result of evaluating an XPath expression
        that compares a non-existent element against
        anything is always false.

More ... http://xfront.com/Be-Careful-Writing-XPath-Expressions-Against-XML-Documents-that-may-have-Non-Existent-Elements.pdf



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