Re: namespace prefixes in XSLT parameters

Bruce R Miller schrieb am 18.09.2012 um 19:10 (-0400):

>   When you pass a parameter to an xslt, for me
> the common issue was always to quote it enough,
> since the value is actually an XPath expression:
>    $stylesheet->transform($document,PARAM=>"'some text'");
>
> I thought I'd get fancy and try using the XPath
> functionality.  I guess it's clear that the XPath
> will be _evaluated_ inside the stylesheet, and
> with the document loaded --- otherwise, it wouldn't
> be much use, right?

I'm surprised. I used to think that wasn't possible. But it is:

my $xslt = XML::LibXSLT->new;
my $proc = $xslt->parse_stylesheet( $xsl_dom );
my $rslt = $proc->transform( $xml_dom, p => '//drei' ); # 'node()'

And it also works from the command line using straight xsltproc:

xsltproc --param p '//text()' x.xsl x.xml

That's not possible using Java Xalan or Saxon 6.5 or 9.2.

Offering this feature, in addition to being handy, does not seem
to be bon-conformant:

http://www.w3.org/TR/xslt#variables

> For example:
>    $stylesheet->transform($document,PARAM=>"//ltx:section/ltx:title/text()");
> 
> What I hadn't anticipated is that it seems to
> get _compiled_ before or outside that context.
> In particular, it doesn't know the namespace prefixes
> that have been established by the stylesheet
> (nor by the document!)

Exactly. Guess it's like when using an XML::LibXML::XPathContext on an
XML::LibXML::Document. You'd have to $xpc->registerNs($prefix, $ns_uri)
what you intend to use.

> And there seems to be no methods to register such
> associations.

Exactly. There doesn't seem to be a documented way of doing so.

No idea how hard it would be to add this feature.

On the other hand, I've never used namespaced parameters, though I seem
to remember they've been recommended to me for use in stylesheets that
you intend to *distribute* to work as part of some customer's workflow.
But I've never gotten that far in the first place …
-- 
Michael Ludwig
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