Re: [xsl] Understanding axis

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Hi Adam,

At 11:32 AM 10/29/2002, you wrote:
> I've been learning the use of axis in transformations and I stumbled on
> something that didn't seem to make sense...
>
> local-name( */* )
> local-name( */child::* )
>
> return the same values.

Yes. XPath */*  and */child::* are both short for XPath child::*/child::*

>  I would have thought...
>
> local-name( */child::* )
> local-name( */*/* )
>
> would be the same (which they aren't).

Nope, they're not. Writing 'child::' does not add a step to the XPath; it 
merely makes explicit the child axis, which the processor assumes by 
default if no other axis is named.

> Could somebody help me reason out why it is this way?

The XPath spec is clear on how all the abbreviations work, though they can 
be a bit tricky to learn since they don't all work the same way (some 
abbreviate an entire step, others only the axis specifier part of a step; 
or in the case of '//', more than a step is abbreviated).

>  This seems to
> complicate scenarios where I would only want certain nodes based upon their
> children without changing context. For instance, something like:
>
> <xsl:for-each select="*/child::*[local-name()=$v]">
> </xsl:for-each>
>
> read as I only want */* where they have a child named $v.

If you want grandchildren elements only that have a child named $v, that's

*/*[*[local-name()=$v]]

If you want child elements only that have a child named $v, that's

*[*[local-name()=$v]]

The latter can be expanded as child::*[child::*[local-name()=$v]]. I'll let 
you expand the first one.

I hope that helps,
Wendell


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
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