Re: [xsl] Selecting the first node set

Subject: Re: [xsl] Selecting the first node set
From: "G. Ken Holman" <gkholman@xxxxxxxxxxxxxxxxxxxx>
Date: Sat, 05 Aug 2006 08:34:51 -0400
At 2006-08-05 12:21 +0100, Fraser Goffin wrote:
Given the following simplified XML instance, can
anyone suggest an expression that will return
ONLY the 'Value' node containing <enum> children
with values A, B and C. I can't rely on the name
of the parent node of <Value> hence I have
deliberately named these as UnknownNameX or any other intervening structure.


/Trade//Value - returns all 3 <Value> nodes /Trade//Value[1] - also returns all 3 <Value> nodes (why is that ?) /Trade//Value[2] - returns nothing (why is that ?)

A number of people have responded already, but from what I can tell, the two that have supplied suggested replacements haven't acknowledged that the <Value> elements are at different depths of the tree. I note that the third <Value> is at level 4 while the other two are at level 3.

So, I suggest that the following will get you the
first <Value> in the document regardless of the depth of the element:


Hugh explained why your prior attempts don't work
... my wording for this is as follows: //Value[1]
won't work because the predicate is bound at the
step level so "//" looks through the entire
document and "Value[1]" which is an abbreviation
for "child::Value[1]" returns the first child
named "Value", so the combination returns "the
first child named Value at every level of the document".

This is a trick question I have had in my
hands-on XSLT training class since 1999 when it
was still combined with DSSSL training.  I've
also see it at conferences where vendors post it
on a white board as a "challenge" to stylesheet
writers to determine who knows their XPath and who doesn't.

I hope this helps, Fraser,

. . . . . . . . . . . . . . Ken

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