Re: [xsl] Excluding a complete branch while identity copying

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Fraser,

You'll be pleased to know that your application is about the easiest 
conceivable task for a near-identity transform.

Start with the identity template:

<xsl:template match="node()|@*">
  <xsl:copy>
    <xsl:apply-templates select="node()|@*"/>
  </xsl:copy>
</xsl:template>

And then simply add a template to match the elements you want to 
discard, which does nothing with the elements it matches:

<xsl:template match="Evens | Squares"/>

-- and you're done. (Well, except for running and testing.)

This "Evens | Squares" template overrides the general-purpose copying 
template for the elements it matches.

Since it does nothing with the matched elements, nothing resembling 
them or their contents appears in the output. The identity template 
matches and copies everything else.

The arrangement of elements in the input doesn't matter since 
template matching doesn't concern itself directly with this, but 
simply reflects the source data in its given order, unless you do 
something to force some reordering.

If this raises questions about the XSLT processing model (why does 
this work?), so much the better, as it's also an excellent 
opportunity to study up on this and learn more about XSLT always works.

Cheers,
Wendell

At 01:44 PM 10/10/2008, you wrote:
> I want to be able to copy a complete XML instance as/is except for
> [say] some specific parts of the input tree. I thought immediately of
> using an identity transform and specifying copy, but how to remove
> those pesky sub-trees :-
>
> Say this was my input :-
>
> <Numbers>
>         <Odds>
>                 <One>1</One>
>                 <Three>3</Three>
>                 <Five>5</Five>
>         </Odds>
>         <Evens>
>                 <Two>2</Two>
>                 <Four>4</Four>
>                 <Six>6</Six>
>         </Evens>
>         <Doubles>
>                 <Two>4</Two>
>                 <Four>8</Four>
>                 <Eight>16</Eight>
>         </Doubles>
>         <Squares>
>                 <Two>4</Two>
>                 <Four>16</Four>
>                 <Eight>64</Eight>
>         </Squares>
> </Numbers>
>
> and I want to copy everything to output except <Evens> and <Squares>.
>
> Lets also assume that the order of the input is undefined, so Evens
> and Squares may/may not be in the positions I have shown above,
> although I can assume that they are both children of <Numbers>.
> Further, I don't know what all the children of Evens and Squares are
> called I just know I don't want them.
>
> Whats the easiest way of accomplishing this ?
>
> many thanks
>
> Fraser.


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Wendell Piez                            mailto:wapiez@xxxxxxxxxxxxxxxx
Mulberry Technologies, Inc.                http://www.mulberrytech.com
17 West Jefferson Street                    Direct Phone: 301/315-9635
Suite 207                                          Phone: 301/315-9631
Rockville, MD  20850                                 Fax: 301/315-8285
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