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RE: statements about a graph (Named Graphs, reification)

From: Michael Schneider <schneid@fzi.de>
Date: Thu, 6 Sep 2007 18:29:08 +0200
Message-ID: <0EF30CAA69519C4CB91D01481AEA06A0374714@judith.fzi.de>
To: "K-fe bom" <u9x3n_15so@hotmail.com>
Cc: <bparsia@cs.man.ac.uk>, <richard@cyganiak.de>, <semantic-web@w3.org>

Hi, Gustavo!

>-----Original Message-----
>From: K-fe bom [mailto:u9x3n_15so@hotmail.com] 
>Sent: Thursday, September 06, 2007 6:13 AM
>To: Michael Schneider; bparsia@cs.man.ac.uk; 
>richard@cyganiak.de; semantic-web@w3.org
>Subject: RE: statements about a graph (Named Graphs, reification)
>
>
>
>>From: "Michael Schneider" <schneid@fzi.de>
>[...]
>>
>>The third candidate is NamedGraphs. But in order to estimate if this
>>approach can be used for the above scenario, I need to know 
>more about it.
>>This was the reason why I asked in my last mail "How do named 
>graph data 
>>get
>>published into the Semantic Web?".
>
>GF> I guess the answer is 'the same way as that of RDF'. The 
>paper "Named 
>Graphs, Provenance and Trust" by Carroll, Hayes, Bizer and 
>Stickler mention

Ok, I'm afraid I did not find the time to fetch and read this document, so I
am going to trust you in the provenance of the following statements about
named graphs. ;-)
 
>RDF/XML as a feasible realization, but with disadvantages: I 
>quote them:
>"Using RDF/XML has disadvantages: [...] The URI at which an 
>RDF/XML document 
>is published is
>used for three different purposes: as a retrieval address, with an 
>operational semantics; 
>as a means of identifying the document; 
>and as a 
>means of identifying the graph described by the document.

The latter is what we are interested in (and what Richard, if I correctly
understood him, was talking about).
 
>There is potential 
>for confusion between these three uses."

Of course! As long as nothing else is said...

>Can I then just go ahead then and assume that every RDF 
>document defines at least one (un)named graph, 
>which is the URI of the document itself?

If you do not have any other contextual information, than you probably have
to assume this - and to be prepared for a possible crash landing. ;-)

But I still seem to not have really understood, what you want to do. You
say:

> I guess what I needed was named graphs with custom reification. 
> I need the grouping feature of named graphs, and I need reification 
> for making statements about the group. 

So, this sounds to me as if you perfectly know the triples, which /you/
yourself want to group in terms of named graphs. Is it this? But in this
case I do not understand why you are interested in the question if you can
"assume that every RDF document defines at least one (un)named graph, which
is the URI of the document itself?". Because then your mission is not
annotating any arbitrary existing graphs, but only the annotation of very
special graphs, which /you/ have defined yourself. And for which /you/ have
defined an URI. This means, you perfectly know that the URIs for such
documents, which contain these triples, have to be interpreted as the named
graphs within. So you simply will not come to the point, where the above
mentioned "potential confusion" would hit you.

But perhaps, I do pretty much misunderstand you here. So can you give any
example?

>>/This/ will of course only be a topic /if/ the above scenario 
>is relevant 
>>at
>>all.
>
>GF> I think it is a very relevant scenario.

Good to hear, thanks! :)

Cheers,
Michael


--
Dipl.-Inform. Michael Schneider
FZI Forschungszentrum Informatik Karlsruhe
Abtl. Information Process Engineering (IPE)
Tel  : +49-721-9654-726
Fax  : +49-721-9654-727
Email: Michael.Schneider@fzi.de
Web  : http://www.fzi.de/ipe/eng/mitarbeiter.php?id=555

FZI Forschungszentrum Informatik an der Universität Karlsruhe
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Received on Thursday, 6 September 2007 16:29:23 UTC

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