RE: Domain-independent GRDDL for RDFa and XSLT restriction on namespaces.

Hi Fabien,

> I quickly scanned the archives of the list and could not find 
> an answer to the following question so I take the risk of 
> asking it again.
> 
> We are using RDFa and GRDDL in SweetWiki [1]: a wiki here 
> persistence is in XHTML+RDFa and navigation is done through 
> SPARQL queries on the RDF extracted from the pages by a GRDDL 
> stylesheet.
> 
> The current stylesheet is domain dependent in the sense that 
> it includes the namespaces of the OWL Lite schemas used in the wiki.
> 
> Before releasing the stylesheet I wanted to make it 
> schema-independent.
> Unfortunately I got stuck by the fact that:
> 1 - RDFa uses standard xmlns attributes to declare its namespaces [2];
> 2 - In XPath "There are no attribute nodes corresponding to 
> attributes that declare namespaces" [3]
>
> Therefore, unless I missed a point, in XSLT I can easily 
> extract property and class QName from XHTML+RDFa and get 
> their ns prefix an local name, but there seems to be no way 
> of accessing the ns declaration (i.e. the URI associated to 
> the prefix) and therefore no way of being independent from 
> the ns used in the RDFa.

XPath 1.0 does have "Namespace Nodes" though

http://www.w3.org/TR/xpath#namespace-nodes

Given a QName as attribute value, I think you can probably get from
QName to XML Namespace Name that way, using something like

<xsl:variable name="prefix" select="substring-before(.,':')"/>
<xsl:value-of select="../namespace::*[local-name()=$prefix]"/>

The "../" is needed because the Namespace Nodes are associated with the
Element Node, rather than the Attribute Node.

(I haven't tried this on RDF/A but I've used variants of it in other
contexts.)

> Did I miss something?
> Is there an RDFa syntax for RDFa ns declaration? e.g.
> <link rel="xmlns:dc" href="http://purl.org/dc/elements/1.1/" 
/> (don't scream; I know it's ugly.)

Pete
---
Pete Johnston
Technical Researcher, Eduserv Foundation
Web: http://www.eduserv.org.uk/foundation/
Email: pete.johnston@eduserv.org.uk 
Tel: +44 (0)1225 474323

Received on Tuesday, 13 June 2006 10:09:35 UTC