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RE: requirement: rdfs query (for lack of a better name...)

From: Jos De_Roo <jos.deroo@agfa.com>
Date: Fri, 7 May 2004 20:29:59 +0200
To: "Pat Hayes <phayes" <phayes@ihmc.us>
Cc: RDF Data Access Working Group <public-rdf-dawg@w3.org>
Message-ID: <OF67605CFD.CA254E25-ONC1256E8D.00633B8A-C1256E8D.00657B72@agfa.com>

BTw Pat, in one of your earlier mails
http://lists.w3.org/Archives/Public/public-rdf-dawg/2004AprJun/0325.html
you wrote ??x and ?y variables and I wondered wether you
intented any difference between 2 kinds of variable ??


PatH wrote:
>> OK Rob, sounds fine...
>> (will sleep over it once more :))
>> sounds like a separation of concerns
>
> Right, exactly, and I think its a good separation.

OK

> Still, unlike Rob, I think that we could reasonably approach the 
> 'inference issue' by seeing if we can come up with some way for a 
> query to indicate to a server (sorry I keep using this term, I can't 
> think of a better one: the engine or entity to which the query is 
> directed and which checks it against a graph: do we have a name for 
> this?)  WHICH graph it wants the query to be directed to. Since 
> 'graph' here can be a virtual graph defined partly by inference 
> closures (and may in fact be infinite in some cases, eg when thinking 
> seriously about datatyped literals), a simple idea like just having a 
> URI for each graph, or one graph per server, seems inadequate. So can 
> we think of a way for a query to indicate which conceptual/virtual 
> graph it is intended to be evaluated with respect to? For example 
> (complete straw man) maybe the query could refer to a source listing 
> a set of rules which the virtual graph is supposed to be closed 
> under, or some such. Or it could be as coarse as just specifying 
> plain/rdf/rdfs/datatyped as options, where each of these refers to a 
> semantic extension and the graph is supposed to be closed under all 
> inferences which are valid wrt that extension.

Right and that's exactly what I have been experimenting with
i.e. when writing a query like e.g. (...and using N3)

(<a-graph-uri> rdfs:).da:from da:select {?A a s:Publication}.

that rdfs: indicates that we have to perform rdfs namespace
entailment and leaving it out of the da:from argument list
doesn't do that (in our tests, we actually map that rdfs: to
http://eulersharp.sourceforge.net/2003/03swap/rdfs-rules.n3
and have similar stuff for xsd: owl: etc... but for those we
don't make any completeness nor decidability claims :))


-- 
Jos De Roo, AGFA http://www.agfa.com/w3c/jdroo/
Received on Friday, 7 May 2004 14:30:47 GMT

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