From: Andy Seaborne <andy.seaborne@talis.com>

Date: Thu, 22 Apr 2010 13:48:57 +0100

Message-ID: <4BD045B9.2070600@talis.com>

To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>

CC: SPARQL Working Group <public-rdf-dawg@w3.org>

Date: Thu, 22 Apr 2010 13:48:57 +0100

Message-ID: <4BD045B9.2070600@talis.com>

To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>

CC: SPARQL Working Group <public-rdf-dawg@w3.org>

Reworded 1 and 4 now in the doc rq25.xml Andy On 20/04/2010 3:47 PM, Birte Glimm wrote: > Here's my new attempt to rephrase condition 4, so that RDF graph > equivalence for answers is hopefully clarified. > > Here's the original condition: > > 4 -- Each SPARQL extension MUST provide conditions, which guarantee > that the answer set for every BGP and AG is uniquely specified up to > RDF graph equivalence, and SHOULD provide further conditions to > prevent trivial infinite answers as appropriate to the regime. > > Here's the proposed change: > > 4 -- Each SPARQL extension MUST provide conditions, which guarantee > that the set of triples obtained by instantiating BGP with each > solution Ī¼ is uniquely specified up to RDF graph equivalence, and > SHOULD provide further conditions to prevent trivial infinite answers > as appropriate to the regime. > > Birte > On 20 April 2010 14:27, Axel Polleres<axel.polleres@deri.org> wrote: >> I am fine with the Condition 1 rewording... >> >> As for 4: >>> 4 -- Each SPARQL extension MUST provide conditions, which guarantee >>> that the answer set for every BGP and AG is uniquely specified up to >>> RDF graph equivalence, and SHOULD provide further conditions to >>> prevent trivial infinite answers as appropriate to the regime. >> >> >> 1) I have a problem with the first part (which actually comes from the original condition 4) >> >> "that the answer set for every BGP and AG is uniquely specified up to RDF graph equivalence," >> >> Can someone tell me what "unique up to RDF graph equivalence" for an answer set actually means? >> RDF graph equivalence is only defined for RDF Graphs, or no? Can't this in the light of Condition 1 just >> be dropped? >> >> 2) I am fine with the remaining part: >> >> "and SHOULD provide further conditions to prevent trivial infinite answers as appropriate to the regime." >> >> Just as an example, why we may be careful with the previous wording suggestion referring to axiomatic triples: >> as to what means "prevent infinite answers from axiomatic triples..."? >> >> e.g. >> >> 1) Is this following infinity "from axiomatic triples"? >> >> Entailment: RIF + RDFS >> >> Graph: >> >> {} >> >> RIF ruleset: >> >> ?X :q 1 :- ?X a rdf:type rdfs:Datatype . >> ?X :q External( ?Y + 1 ):- ?X :q ?Y >> ?Z rdf:type :c :- And( ?X :q ?Y >> External( pred:iri-string( ?Z concat("rdf:_" ?Y) ))) >> >> Query: >> >> SELECT ?X WHERE { ?X rdf:type :c } >> >> Answer: >> rdf:_1 >> rdf:_2 >> ... >> >> Answer: >> >> >> 2) Is this following infinity "from axiomatic triples"? >> >> Entailment: RDFS >> >> Graph: >> rdfs:ContainerMembershipProperty rdfs:subClassOf :c >> >> Query: >> >> SELECT ?X WHERE { ?X rdf:type :c } >> >> Answer: >> rdf:_1 >> rdf:_2 >> ... >> >> best, >> Axel >> >> On 19 Apr 2010, at 11:46, Birte Glimm wrote: >> >>> Hi all, >>> following up on the proposed changes to the extensions of BGP >>> matching, I would suggest the following. The first condition is >>> changed from >>> 1 -- The scoping graph, SG, corresponding to any consistent active >>> graph AG is uniquely specified and is E-equivalent to AG. >>> to >>> 1 -- The scoping graph, SG, corresponding to any consistent active >>> graph AG is specified uniquely up to RDF graph equivalence and is >>> E-equivalent to AG. >>> Then we have made it explicit that differences in bnode labels only are ok. >>> >>> The second change regarding finiteness is more tricky. I'll try what >>> Andy suggested, which leaves it to the entailment regimes to identify >>> appropriate conditions and suggest to change from >>> 4 -- Each SPARQL extension must provide conditions on answer sets >>> which guarantee that every BGP and AG has a finite set of answers >>> which is unique up to RDF graph equivalence. >>> to >>> 4 -- Each SPARQL extension MUST provide conditions, which guarantee >>> that the answer set for every BGP and AG is uniquely specified up to >>> RDF graph equivalence, and SHOULD provide further conditions to >>> prevent trivial infinite answers as appropriate to the regime. >>> >>> Maybe we can discuss and hopefully agree on that in tomorrow's teleconf. >>> Cheers, >>> Birte >>> >>> >>> -- >>> Dr. Birte Glimm, Room 306 >>> Computing Laboratory >>> Parks Road >>> Oxford >>> OX1 3QD >>> United Kingdom >>> +44 (0)1865 283529 >>> >>> >> >> > > > > -- > Dr. Birte Glimm, Room 306 > Computing Laboratory > Parks Road > Oxford > OX1 3QD > United Kingdom > +44 (0)1865 283529 > > > Please consider the environment before printing this email. > > Find out more about Talis at http://www.talis.com/ > shared innovationā¢ > > Any views or personal opinions expressed within this email may not be those of Talis Information Ltd or its employees. The content of this email message and any files that may be attached are confidential, and for the usage of the intended recipient only. If you are not the intended recipient, then please return this message to the sender and delete it. Any use of this e-mail by an unauthorised recipient is prohibited. > > Talis Information Ltd is a member of the Talis Group of companies and is registered in England No 3638278 with its registered office at Knights Court, Solihull Parkway, Birmingham Business Park, B37 7YB.Received on Thursday, 22 April 2010 12:49:18 UTC

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