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Re: Want GRDDL intro for WG-dummies :)

From: Rinke Hoekstra <hoekstra@uva.nl>
Date: Fri, 9 May 2008 11:06:17 +0200
Cc: "Ivan Herman" <ivan@w3.org>, "OWL Working Group WG" <public-owl-wg@w3.org>
Message-Id: <A1FDCC6B-A412-44A8-AF77-FB44BEADEAB6@uva.nl>
To: "Michael Schneider" <schneid@fzi.de>

Hi Michael,

On 9 mei 2008, at 10:46, Michael Schneider wrote:
> Ok, then I will put a deliberately provocative question:
> What *is* GRDDL actually?

A standard way to indicate that there exists some transformation from  
(essential information encoded in) the source XML format to RDF. In a  
round-about way it is a means to express arbitrary RDF in XML.

> I can define an XSLT between two XML formats, anyway.
> Is GRDDL more than just a hint to people that they can
> use XSLT to transform arbitrary XML to *RDF/XML* in particular?

Yes, GRDDL does not require you to use XSLT, it can be a web service  
as well (cf. Bijan's remark on the telecon). But to answer the gist of  
your question: in principle yes, because GRDDL allows you to specify  
multiple transformations that each extract different information from  
the XML. It's about 'gleaning' not translation. I.e. given a  
particular XML file, give me the particular RDF triples encoded in  
this XML that I can understand.

> Or putting it differently: What would be missing,
> if GRDDL wouldn't exist, given that there is already XSLT?

1) Because the application of an XSLT transformation is not guaranteed  
to produce RDF
2) Because GRDDL allows transformations other than those expressed in  
XSLT (XSLT is not a very powerful language)

> Or putting it even more differently: What would be wrong with
> just defining *some* XSLT from OWL/XML to RDF/XML,
> simply forgetting about the *word* "GRDDL"?

Because that's not what we're after... or maybe: that's exactly the  
issue we have been debating. A requirement most (if not all) WG  
members share is that *if* we have an OWL/XML format it should be  
translateable to RDF/XML (or RDF) in a standard way. We need some way  
to point to this official transformation: this is what GRDDL  
standardises, and allows us to do. 'Just' a pointer to an XSLT does  
not do the same thing.



Drs. Rinke Hoekstra

Email: hoekstra@uva.nl    Skype:  rinkehoekstra
Phone: +31-20-5253499     Fax:   +31-20-5253495
Web:   http://www.leibnizcenter.org/users/rinke

Leibniz Center for Law,          Faculty of Law
University of Amsterdam,            PO Box 1030
1000 BA  Amsterdam,             The Netherlands
Received on Friday, 9 May 2008 09:07:03 UTC

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