On 21/01/2008, Jesper Tverskov <jesper(_at_)tverskov(_dot_)dk> wrote:
The old way even has the power and fascination of being just one
template, the identity template. This is how the identity template
looks in two specs, in hundreds of books, in thousands of articles and
tutorials, and in millions of XSLT stylesheets until this very day.
Why change things for the worse just to confuse people?
Well the standard identity template is completely non-intuitive in
itself... so I think most new XSLT'ers are confused enough by it. I
remember in the early days cutting and pasting it the first few times
I needed it just because it seemed so strange and hard to reproduce by
hand. Having something within xsl:copy was the hardest thing to
comprehend, iirc.
Anyway, this thread was about understanding a little better how the
identity template processes attributes.
For example, try this with Saxon:
<xsl:template match="@*">
<xsl:copy>
<xsl:apply-templates select="@*|node()"/>
</xsl:copy>
</xsl:template>
You get the warning:
"The child axis starting at an attribute node will never select anything"
The apply-templates call is effectively redundant for some of the
node() kinds... so why leave it in? From a human perspective it's
nice and compact, but from a processing perspective it's odd. Compact
code is a hackers dream and a maintainers nightmare, so its not
something to necessarily aspire to.
A less compact but possibly more intuitive indentity transform is the
one Mike suggested right at the beginning:
<xsl:template match="element()">
<xsl:copy>
<xsl:apply-templates select="@*,node()"/>
</xsl:copy>
</xsl:template>
<xsl:template match="attribute()|text()|comment()|processing-instruction()">
<xsl:copy/>
</xsl:template>
Had that been the one that I learnt, I might have realised sooner that
attributes don't have children (and I might have understood the whole
thing a little quicker).
As the original identity template is ingrained in my mind though I'll
continue to use that - along with the "@*, node()" modification.
--
Andrew Welch
http://andrewjwelch.com
Kernow: http://kernowforsaxon.sf.net/
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