W3C home > Mailing lists > Public > public-rdf-in-xhtml-tf@w3.org > March 2005

Re: GRDDL in non-HTML XML - how, exactly?

From: Chris Lilley <chris@w3.org>
Date: Wed, 23 Mar 2005 20:33:40 +0100
Message-ID: <1382178654.20050323203340@w3.org>
To: Dan Connolly <connolly@w3.org>
Cc: RDF in XHTML task force <public-rdf-in-xhtml-tf@w3.org>

On Wednesday, March 23, 2005, 8:11:33 PM, Dan wrote:

DC> On Mon, 2005-03-21 at 15:55 +0100, Chris Lilley wrote:
>> Hello public-rdf-in-xhtml-tf,
>> In section 3 of GRDDL (I was reading the 13 April 2004 version)
>> http://www.w3.org/TR/grddl/#grddl-xml
>> The first two paragraphs seem to contradict each other
>> >> The GRDDL profile mechanism is a special case of GRDDL designed to
>> >> fit within the syntax of XHTML 1.0. The general form of GRDDL is an
>> >> attribute suitable for use with a wide variety of XML dialects.
>> OK, cool, so I read on to find out how to do that ...
>> >> Use of the interpreter attribute in the
>> >> http://www.w3.org/2003/g/data-view# namespace on the root element of
>> >> an XML document indicates that RDF statements that result from
>> >> transformation of the HTML document to RDF by designated algorithms
>> >> are part of the document's meaning.
>> "the HTML document"? What if my XML is *not* HTML? Is 'the HTML
>> document' just a typo?

DC> yes... fixed in
DC>  http://www.w3.org/2004/01/rdxh/spec#grddl-xml
DC>  $Revision: 1.58 $


>> To be specific, how would I change this example
>> http://www.w3.org/TR/SVG11/metadata.html#Example
>> to say that the content of the metadata element is part of the documents
>> meaning? Do I merely add
>> xmlns:grddl="http://www.w3.org/2003/g/data-view#"
>> grddl:interpreter="what, exactly, goes here"

DC> yes...

DC>    xmlns:data-view="http://www.w3.org/2003/g/data-view#"
DC> data-view:transformation="http://www.w3.org/2003/g/embeddedRDF.xsl"

Ok so transformation, not interpreter.

DC> You can see the result at
DC>   http://www.w3.org/2003/g/svgc-ex/svg_meta_ex.svg
DC> It works with http://www.w3.org/2003/g/svgc-ex/glean.py ala...

DC> $ python glean.py --output ,svgm.rdf
DC> http://www.w3.org/2003/g/svgc-ex/svg_meta_ex.svg

DC> xsltproc spews complaints about the SVG namespace document
DC> (it's HTML, not XHTML)

Really? (goes to fix that)

DC>  but you can disregard those diagnostics;
DC> the resulting ,svgm.rdf has the right answer. (I hope we'll
DC> upgrade the SVG namespace document to RDDL or the like soon.)

Yes, good idea.

DC> I tried it in the online service...
DC>   http://www.w3.org/2004/01/rdxh/grddl-xml-demo
DC> but I it fails in a way that I don't understand. (Dom?)

>> I read
>> >> The value of the grddl:interpreter attribute designates a list of
>> >> algorithms by URI reference
>> It seems to point to an xsl stylesheet, not a list of algorithms.

DC> As Dom explained, an XSLT stylesheet is a representation of
DC> an algorithm.

An, yes - its not a list, or at least, only a very short one.

>> I would also like to know how to GRDDLize these examples
>> http://www.w3.org/TR/SVG11/coords.html#GeographicCoordinates
>> if that turns out to be different.

DC> Not much. I did the 1st and 2nd ones...
DC> http://www.w3.org/2003/g/svgc-ex/coord_meta1.svg
DC> http://www.w3.org/2003/g/svgc-ex/coord_meta2.svg

DC> On the 3rd one I get an RDF parsing error...

DC> RDF.RedlandError: property element 'CoordinateReferenceSystem' has
DC> multiple object node elements, skipping.

Hmm. Is that an issue with your code or an issue with our RDF?

>> Please note also that SVG is structured, so a single SVG document
>> instance can have several logical parts and each of these can have its
>> own metadata element. How do I indicate that the metadata applies to
>> just a particular part of the document (ie, the parent of the metadata
>> element?

DC> RDF is context-free... the subjects of the statements are explicit.
DC> the rdf:about attribute is used to say what statements are about.

DC> In the 2nd example, I see this bit of RDF:

DC>         <rdf:Description>
DC>           <!-- In case of a well-known Coordinate Reference System
DC>                an 'Identifier' is enough to describe the CRS -->
DC>           <crs:CoordinateReferenceSystem
DC> svg:transform="rotate(-90) scale(100, 100)">
DC>             <crs:Identifier>

DC> That just says "there is a coordinate reference system." It doesn't
DC> say what the relationship between that coordinate system and this
DC> SVG file is.

Suggestions on how to fix that? Its supposed to say 'here is a
coordinate system' and 'here is a projection' and 'this svg file
represents a map in that coordinate system with that projection'. It
seems we are missing the RDFese, or the GRDDLese, to make the third

 Chris Lilley                    mailto:chris@w3.org
 Chair, W3C SVG Working Group
 W3C Graphics Activity Lead
Received on Wednesday, 23 March 2005 19:33:42 UTC

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