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Re: Re 2: [TF-ENT] Querying datasets with default plus named graphs

From: Ivan Herman <ivan@w3.org>
Date: Mon, 12 Oct 2009 15:52:03 +0200
Message-ID: <4AD33483.7070801@w3.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
CC: SPARQL Working Group <public-rdf-dawg@w3.org>


Hey Birte,

[skip]

>> This may not be a problem, but I must add that if this is what we mean
>> than this means RDFS reasoning on named graphs fairly difficult to use.
>> What this means that a specific named graphs should always include both
>> the vocabulary part _and_ the data itself (this is where the missing
>> import mechanism backfires). Indeed, for the default graph, I can have
>> as many FROM statements as I want, some of those getting hold of the
>> vocabulary and others of the data, this is not a possibility for a named
>> graph... Or do I miss something again?
> 
> That is how I also understand it. Named graphs are only useful under
> entailment regimes if they include schema/TBox/vocabulary part and the
> data. That is a limitation and it is hard for me to judge how big a
> limitation that is in practise. Axel did send a link to some proposal
> for a language extension to fix this, but this has an effect on the
> general query language and is no longer limited to entailment regimes.
> For a FPWD my suggestion would be to clearly identify the status as is
> (limited usefulness of named graphs) and pointers to solutions how
> this could be fixed (either as concrete suggestions for extension
> marked at risk or just an informative suggestion of future
> extensions).
>

I agree, this should be noted in the document and leave it there for
now. That is why we have public reviews, after all...

Thanks!

Ivan

P.S. B.t.w.: I am an official reviewer for the document, but I am not
sure when you feel that it is ready to be reviewed... So I wait for your
'go'!


>> As I said, we may want to live with this, but it is worth noting to
>> ourselves...
> 
> Definitely it should be noted.
> Birte
> 
>> Ivan
>>
>> --
>>
>> Ivan Herman, W3C Semantic Web Activity Lead
>> Home: http://www.w3.org/People/Ivan/
>> mobile: +31-641044153
>> PGP Key: http://www.ivan-herman.net/pgpkey.html
>> FOAF: http://www.ivan-herman.net/foaf.rdf
>>
> 
> 
> 

-- 

Ivan Herman, W3C Semantic Web Activity Lead
Home: http://www.w3.org/People/Ivan/
mobile: +31-641044153
PGP Key: http://www.ivan-herman.net/pgpkey.html
FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Monday, 12 October 2009 13:52:32 GMT

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