Re: [xsl] Seeking combinatorial XPATH

[Jeni Tennison <mail at jenitennison dot com>]

Hi Paul,

I think that you want:

  * any A element such that
    either
      * the string value of its child B element
        * whose num attribute equals 'case1'
      equals
      * the string value of the B element
        * that is a child of any A element
        and
        * whose num attribute equals 'case3'
    or
      * the string value of its child B element
        * whose num attribute equals 'case3'
      equals
      * the string value of the B element
        * that is a child of any A element
        and
        * whose num attribute equals 'case1'

This translates as:

  A[B[@num = 'case1'] = /ROOT/A/B[@num = 'case3'] or
    B[@num = 'case3'] = /ROOT/A/B[@num = 'case1']]

You may find it handy to store the A elements in keys based on the
value of their B children (with the different @nums):

<xsl:key name="case1" match="A" use="B[@num = 'case1']" />
<xsl:key name="case3" match="A" use="B[@num = 'case3']" />

With these definitions you can retrieve all the A elements whose B
child (with a num attribute equals to 'case1') equals 'abc' with:

  key('case1', 'abc')

If none are retrieved from the key, then there aren't any A elements
with the relevent B child with that value and the expression will
evaluate to false in a boolean context. So, you can change the
expression to:

  A[key('case3', B[@num = 'case1']) or
    key('case1', B[@num = 'case3'])]

[Note: You hardly ever want to use the text() node test to get text
nodes - more often than not, you want the string value of the node
instead, which you can just get by selecting the node itself.]

I hope that helps,

Jeni

---
Jeni Tennison
http://www.jenitennison.com/



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