Re: [xsl] Applying a transform to a tranform

[Wendell Piez <wapiez@xxxxxxxxxxxxxxxx>]

Hi Todd,

It is possible in XSLT 1.0 only if you use your vendor's node-set() 
extension, which is designed specifically for this purpose. Most processors 
have this extension function available in some form: check your 
documentation. In particular, you might look into whether yours supports 
functions in the EXSLT namespace ("Extended XSLT", an effort of several 
well-regarded members of our community, see http://exslt.org), which is 
even a semi-portable version.

In XSLT 2.0 the conversion of result-tree-fragment to node-set, which is 
what this function does, is transparent: you won't even have to think about it.

To do what you want to do using the EXSLT version:

<xsl:stylesheet version="1.0"
    xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
    xmlns:exslt="http://exslt.org/common";
    extension-element-prefixes="exslt">

<xsl:variable name="first-process-results">
  <!-- you'll want either an explicit path here, or better, a
       mode, to avoid infinite recursion -->
  <xsl:apply-templates select="/rowset" mode="first"/>
</xsl:variable>

... then your normal templates in the mode "first" ...

And then your actual transform:

<xsl:template match="/">
  <xsl:apply-templates select="exslt:node-set($first-process-results)"
    mode="second"/>
</xsl:template>

... and your second-pass templates in the mode "second"....

Basically what this is doing is processing the document in one mode, 
binding the result to a variable (in XSLT 1.0 it's a "result tree 
fragment"), then the stylesheet processes this fragment, turning it into a 
node set using the extension function.

You don't have to use modes, but you might be sorry if you try it without. :->

At 05:04 PM 9/9/2003, you wrote:
> I thought the following logic would work but it doesn't
>
> <xsl:apply-templates select="rowset"/>  -- to transform into tree like xml
> <xsl:apply-templates select="tree"/> -- to transform into html tree control

In the context where you invoke these, the second apply-templates has no 
way to know you don't mean "child::tree" (XPath "tree" = XPath 
"child::tree"), but rather the results of the first apply-templates. It's 
only doing what you're telling it to (processing the tree children of the 
context node).

> It appears as though this is transforming the original doc in both instances
> (i.e. the rowset template select doesn't "pass" the results of its transform
> forward).

No, and it'd be pretty bizarre if it did, without your even asking. (Where 
would it all end? :-> )

Anyhow, try a node-set() function and see how it works.

Cheers,
Wendell


======================================================================
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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