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Re: Signalling entailment in queries

From: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
Date: Wed, 21 Jul 2010 10:46:33 +0100
Message-ID: <AANLkTilhx3M4to5Yh3Rmxj-Xb-p8fadoSISdHJrUQLb1@mail.gmail.com>
To: Sandro Hawke <sandro@w3.org>
Cc: SPARQL Working Group <public-rdf-dawg@w3.org>
[snip]
[snip]
>> > It's tempting to also allow parameterization of the entailment regime,
>> > perhaps like this:
>> >
>> >    PREFIX ent <http://www.w3.org/ns/entailment/>
>> >        SELECT * FROM NAMED <g1>
>> >        WHERE { GRAPH <g1> ENTAILS BY ent:RDFS { ?x
>> >        rdfs:subClassOf ?y } }
>>
>> I think this is an abuse of prefix that we shouldn't allow. Prefix is
>> a directive for the parser to enable the expansion of abbreviaed IRIs
>> into fully qualified ones. I would not want to overload this with a
>> specification for entailments, which has nothing to do with parsing or
>> IRI expansion. I do like a keyword, but it would have to be one that
>> is not yet used in SPARQL I think.
>
> I think you're misunderstanding me here.   I'm using PREFIX exactly as
> you say -- as a shorthand allowing abbreviation of IRIs.  I just happen
> to be using it for abbreviating the IRI of an entailment regime, just
> like you did in an example above. If you don't use PREFIX, it looks like
> this:
>
>        SELECT * FROM NAMED <g1>
>        WHERE { GRAPH <g1> ENTAILS BY
>        <http://www.w3.org/ns/entailment/RDFS> { ?x
>        rdfs:subClassOf ?y } }

You are absolutely right. I overlooked the ENTAILS BY part and got the
impression that it is the prefix that decides the entailment. Sorry
for that. I am happy with what you suggested now that I see both bits.
Birte


>  -- Sandro
>
>> > I understand this parameterization is similar to the out-of-scope
>> > "Parameterized Inference" feature [1], but perhaps if it's really as
>> > simple as this, it's okay to do anyway.   (If not, is there a way to
>> > suggest that everyone implement it the same way, even if it's not in the
>> > spec?  :-)
>>
>> I would be happy for either (having a keyword despite it being out of
>> scope or an informal agreement). With an informal agreement it is,
>> however, not forbidden to do inferences no matter whether the chosen
>> keyword has been used or not.
>>
>>
>> Birte
>>
>>
>> > Finally, I wanted to thank folks for reminding me of the incorrectness
>> > of thinking of the entailments of a graph as another graph.  Under
>> > entailment regime E, graph G will entail graphs G0, G1, ... Gn, rather
>> > than a single graph GE.  In many simple cases, the merge of G0...Gn is
>> > also entailed and can be used as the single graph-of-all-entailments,
>> > but in cases with disjunction, such a union is not itself entailed, so
>> > there is no graph-of-all-entailments.  (I've learned and forgotten this
>> > too many times, sorry.)
>> >
>> >
>> > One more thought -- I'm not sure the word "entails" is the best word
>> > here.  Perhaps "IMPLIES" would make more sense to relevant audience.
>> >
>> >    -- Sandro
>> >
>> > [1] http://www.w3.org/2009/sparql/wiki/Feature:ParameterizedInference
>> >
>> >
>> >
>> >
>>
>>
>>
>
>
>



-- 
Dr. Birte Glimm, Room 309
Computing Laboratory
Parks Road
Oxford
OX1 3QD
United Kingdom
+44 (0)1865 283520
Received on Wednesday, 21 July 2010 09:47:07 GMT

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