Re: Using XML::LibXML::SAX::Parser as replacement for XML::LibXML::SAX::Generator

On Wednesday 7. April 2010 14:52:57 The Distinguished Dahut Robin wrote:

> Heh. Possibly the hardest thing in XML is picking the right tool for any
>  given task. There are cases in which using XSLT is a PITA, and others
>  where it shines; and the same applies to pretty much anything else.

Yup :-)

> It does indeed look like your case requires more processing than I'd be
>  happy to do with XSLT, so something Perl-based sounds good.

OK, good! :-)


> Actually, the primary reason why XSLT is a bad match is mostly because
>  it doesn't have any SPARQL support, and limited HTTP support (only the
>  simplest GETs). If you were getting information in XML from given URIs
>  in the source document, you could rather easily use XSLT for this task
>  (with the document() function).

Right!

> >> Kjetil: do you have some code to show us so we could advise options?
> >
> > Sure! My RDF::RDFa::Template module (not yet on CPAN) is the example
> > :-) More specifically, it would be great if you had a look at the
> > current SAX Filter:
> > http://svn.kjernsmo.net/RDF-RDFa-Template/trunk/lib/RDF/RDFa/Template/
> >SAXFilter.pm
> 
> So, this is not at all a complete port of your code, it's just an
>  example of how it can be done with Perl using XPath to power the
>  transformations:

Great, thanks! I've actually just released my code:
http://search.cpan.org/dist/RDF-RDFa-Template/
but with a long TODO list. :-) It would be great if people poked at it, the 
idea is to make it easy to create simple Semantic Web driven pages. It is 
an early alpha/proof-of-concept/discussion item kinda thing now, but all 
the more reason to poke at it :-)

Anyway, on the top of the TODO-list is the fact that I need something to 
treat SPARQL queries with more than one solution, so I need to do some 
looping and stuff. I think I will revisit your code when I need to solve 
this problem.

> Assuming your namespace declarations are all on the root element, that
>  $doc holds the Document, and that the namespace isn't used by any
>  attribute or element in the context (it would still work, but you'd be
>  getting side-effects), the following should work:

Actually, switching to X:L:SAX::Parser was a decent solution.
 
> > the doctype declaration,
> 
> Still assuming $doc holds the Document, with $root from above, and
>  $pubId and $sysId retrieved from the proper places:
> 
> $doc->setExternalSubset($doc->createExternalSubset($root->tagName,
>  $pubId, $sysId));

Hmmm, I tried 
my $xpc = XML::LibXML::XPathContext->new($orig);
$xpc->registerNs('rat', $self->{DOC}->{RATURI});
$xpc->registerNs('xhtml', 'http://www.w3.org/1999/xhtml');
my ($system_id) = $xpc->findnodes('/xhtml:html/@rat:doctype-system') || 
'http://www.w3.org/MarkUp/DTD/xhtml-rdfa-1.dtd';
my ($public_id) = $xpc->findnodes('/xhtml:html/@rat:doctype-public') || 
'-//W3C//DTD XHTML+RDFa 1.0//EN';
my $dtd = XML::LibXML::Dtd->new($public_id, $system_id); 
my $output = $builder->result;
$output->setExternalSubset($dtd);

But that took ages to run, and I assumed that XML::LibXML::Dtd tried to 
download the resource identified by the system ID... Does your code do the 
same thing? I just want to prefix the string... :-)



> > and finally, package a simple
> > HTTP::Server::Simple script for people to try it out.
> 
> For that, you're on your own :)

Actually, it was very easy! :-)
 
Cheers,

Kjetil
-- 
Kjetil Kjernsmo
[email protected]
http://www.kjetil.kjernsmo.net/
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