Re: sxml-match patterns

Hello!

	This is a reply to a message by Alessandro Colomba 
on the webit-discuss mailing list:
  http://sourceforge.net/mailarchive/forum.php?thread_id=7330228&forum_id=15740

The message might be of interest to other SXML users.

Alessandro Colomba wrote:

> Attempting to write a stylesheet to walk through an entire document,
> and match inner elements, I could not find a way to express something
> like:
>
> <!-- the identity transform -->
> <xsl:template match="@*|node()">
>   <xsl:copy>
>     <xsl:apply-templates select="@*|node()"/>
>   </xsl:copy>
> </xsl:template>
> Initially, wanting to copy a tree and transform only select elements,...

It may be helpful to exploit the strengths of traversal and matching
(querying). Although you can use traversal for querying/matching (by
mapping non-matched or uninteresting elements to nothing) and
querying/matching for bulk transformations, that doesn't seem to be
the best use of either tool. The identity transform has the following
simple form in SXSLT:

	(pre-post-order sxml
	 `((*text* . ,(lambda (tag str) str))
	   (*default* . ,(lambda node node))))

You can add more rules to transform some nodes differently. Please see
examples in SSAX/examples (in the CVS repository or in a SSAX
distribution). In particular, sxml-nesting-depth-label.scm

It should be stressed that each SXSLT handler receives a node. So, a
handler can use sxml-match to match/transform just that particular
node. You can leave the rest of the traversing to pre-post-order
engine.

If you're interested in translating XSLT stylesheets, you might want
to take a look at STX,
	http://www196.pair.com/lisovsky/transform/stx/
and	http://www196.pair.com/lisovsky/query/


	Cheers,
	Oleg


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