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RE: Multiple GRDDL results in a single transform??? GRDDL and Named Graphs

From: Booth, David (HP Software - Boston) <dbooth@hp.com>
Date: Fri, 18 Jan 2008 15:57:06 +0000
To: Jeremy Carroll <jjc@hpl.hp.com>, "public-grddl-wg@w3.org" <public-grddl-wg@w3.org>
CC: "patrick.stickler@nokia.com" <patrick.stickler@nokia.com>, "chris@bizer.de" <chris@bizer.de>, Phil Archer <parcher@icra.org>
Message-ID: <184112FE564ADF4F8F9C3FA01AE50009DECDA1AFAD@G1W0486.americas.hpqcorp.net>

In http://www.w3.org/2007/OWL/wiki/POWDER
I am taken aback by this statement:
"By the operation of GRDDL, then every POWDER document has two GRDDL results: itself (being an RDF/XML document), and the result of the POWDER transform applied to that document."

In the GRDDL WG I remember pursuing the question of whether an RDF/XML document could have a GRDDL transformation (by virtue of being XML) in addition to the identity transformation defined by the GRDDL spec:
"If an information resource IR is represented by a conforming RDF/XML document[RDFX], then the RDF graph represented by that document is a GRDDL result of IR."

I remember being told that it is not possible: the RDF/XML syntax does not allow the grddl:transformation attribute to be specified on the root element.  Indeed, the RDF validator at
confirms this.  When I feed this supposedly RDF/XML into the validator:
<?xml version="1.0"?>
<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
  <rdf:Description rdf:about="http://www.w3.org/">
    <dc:title>World Wide Web Consortium</dc:title>
The validator reports: "Error: {E201} Illegal attributes on rdf:RDF[Line = 6, Column = 2]"

How exactly is POWDER proposing to gain this additional GRDDL transformation?

David Booth, Ph.D.
HP Software
+1 617 629 8881 office  |  dbooth@hp.com

Opinions expressed herein are those of the author and do not represent the official views of HP unless explicitly stated otherwise.

> -----Original Message-----
> From: public-grddl-wg-request@w3.org
> [mailto:public-grddl-wg-request@w3.org] On Behalf Of Jeremy Carroll
> Sent: Thursday, January 17, 2008 1:43 PM
> To: public-grddl-wg@w3.org
> Cc: patrick.stickler@nokia.com; chris@bizer.de; Phil Archer
> Subject: Multiple GRDDL results in a single transform???
> GRDDL and Named Graphs
> Summary:
> - XSLT2 supports multiple output documents, is each a GRDDL result?
> - With a document with multiple GRDDL results can we regard each as a
> graph in a named graph approach (particularly if each GRDDL result is
> given a different base URI somehow, e.g. in an XSLT2 result-document
> instruction)
> - Can different GRDDL results for the same document be treated with
> different pragmatic force (e.g. the end-user acts on some of the GRDDL
> results while ignoring others, perhaps in a systematic way)
> - Note it is possible to do this with XSLT1, and some trickery
> ===========
> I am looking at POWDER, and thinking about using GRDDL to convert a
> simpler form into a more complicated form.
> The idea is that the simpler form would be more suited to operational
> processing, but the more complex form would have a fuller statement of
> the formal semantics, that underwrites the operational semantics.
> The page on which I am working is:
> http://www.w3.org/2007/OWL/wiki/POWDER
> One issue is that a typical POWDER document consists of one DR
> (description of resources or something). Some POWDER documents consist
> of more than one DR.
> A DR typically specifies the following:
>    - validity dates, during which it is claimed
>    - a set of resources defined by matching various properties of URIs
>    - properties that each of those resources are claimed to
> have, while
> the DR is valid (e.g. being pornographic)
> Thus a DR can be seen as claiming a rdfs:subClassOf
> relationship, during
> validity dates.
> One way of handling this, in the single DR case, is to include the
> subClassOf in the GRDDL result, make the validity dates refer to the
> document itself (the information resource), so that outside
> the validity
> period the GRDDL result says that it is invalid, and hence
> shouldn't be
> believed; whereas during the validity period, the subClassOf triple is
> asserted.
> /// aside
> Another way of handling this is to move all the complexity of validity
> and subClassOf etc. into the text of the definition of DR, and use a
> 'semantic extension' as the formal implementation ....
> /// i don't really like that, since it's pushing the maths past its
> design  limitations.
> ====
> Here is an XSLT1 implementation sketch, for multiple DRs in a
> single file.
> The namespace is used to encode (an upper bound for) the
> number of DRs.
> e.g.
> http://example.org/powder?10
> can have no more than 10 DRs in it, whereas
> http://example.org/powder?1000
> can have 1000 DRs
> The GRDDL result for
> http://example.org/powder?N
> provides N different GRDDL transforms for the namespace, the i-th
> transform selecting the i-th DR in the document and transforming it.
> The result of the i-th transform includes the validity triples for the
> ith DR and the subClassOf triple, which should only be believed if the
> DR is valid.
> The intended reading is that the GRDDL results including
> invalid DRs are
> filtered, and only the GRDDL results with valid DRs are beleived.
> One way of achieving this is to attach the validity to the information
> resource itself, e.g. a GRDDL result of
>    <rdf:Description rdf:about="">
>       <wdr:validFrom>2007-01-01</wdr:validFrom>
>       <wdr:validUntil>2007-07-07</wdr:validUntil>
>    </rdf:Description>
> would describe a current invalid information resource, and hence,
> pragmatically not useful.
> In this way, an application would have many different GRDDL results,
> some describing a valid information resource, some not, and it is
> expected to act on the merge of the GRDDL results describing a valid
> information resource.
> Jeremy
Received on Friday, 18 January 2008 15:58:12 UTC

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