RE: [xsl] The identity transform and attributes

["Michael Kay" <mike@xxxxxxxxxxxx>]

I wouldn't expect any measurable performance difference, but if you feel it
adds clarity (or reusability) then go ahead. Perhaps even more logical would
be:

<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> 

(The "," in place of "|" is a minor optimization that recent Saxon releases
do anyway - it avoids an unnecessary merge/deduplication of the sequence of
attributes with the sequence of children.)

Michael Kay
http://www.saxonica.com/

> -----Original Message-----
> From: Andrew Welch [mailto:andrew.j.welch@xxxxxxxxx] 
> Sent: 21 January 2008 10:29
> To: xsl-list@xxxxxxxxxxxxxxxxxxxxxx
> Subject: [xsl] The identity transform and attributes
> 
> I'm wondering if the default identity transform should be this:
> 
> <xsl:template match="@*|node()">
>     <xsl:copy>
>         <xsl:apply-templates select="@*|node()"/>
>     </xsl:copy>
> </xsl:template>
> 
> Or this:
> 
> <xsl:template match="node()">
>     <xsl:copy>
>         <xsl:apply-templates select="@*|node()"/>
>     </xsl:copy>
> </xsl:template>
> 
> <xsl:template match="@*">
>     <xsl:copy/>
> </xsl:template>
> 
> The former is nice and compact, but when the node is an 
> attribute node does the apply-templates call have any effect 
> - even if it's a few clock cycles wasted?  It's a pointless 
> instruction at that point.  I guess it is too for non-element 
> node()'s such as whitespace?
> 
> Also, the shallow copy copies the entire attribute, so there 
> is no opportunity to override the text() of the attribute.  
> The only way is to add a separate matching template for the 
> attribute - the latter perhaps makes this a little clearer.
> 
> A useful distinction or a waste of time? :)
> 
> cheers
> --
> Andrew Welch
> http://andrewjwelch.com
> Kernow: http://kernowforsaxon.sf.net/