- From: Axel Polleres <axel.polleres@deri.org>
- Date: Fri, 5 Mar 2010 13:33:59 +0000
- To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>
- Cc: "Andy Seaborne" <andy.seaborne@talis.com>, <ivan@w3.org>, <public-rdf-dawg@w3.org>
On 5 Mar 2010, at 11:27, Birte Glimm wrote: > Good question indeed. My feeling is, that it is not an entailment > regime, but rather another source of infinite answers from datatype > aware systems. Datatype aware systems as Andy sketches them will not give infinite answers, but just return the canonical representations for each datatype, or do I miss something? best, Axel > For OWL Direct Semantics, this is covered since there we only return > asserted data values modulo sub-property entailment. This assumes that > the original lexical form is returned. Internally we canonicalise > everything (otherwise you cannot do reasoning with facets etc > correctly), but we keep the original lexical form anyway to not > confuse users by silently changing their data values even if it is to > something equivalent. > For D-Entailment/OWL RDF-Based Semantics, I am not quite sure what the > best solution would be. At the moment, I restrict bindings to values > that occur in the skolemised scoping graph. This guarantees > finiteness. What is not clear to me is whether that restricts systems > so that they have to return the original lexical form or whether the > scoping graph is whatever systems build from the input when they parse > it. My feeling is that systems can do what they prefer since in any > case the result is graph equivalent to the active graph and even for > the active graph I am not sure whether anything defines what the > active graph actually contains after parsing a document with such > datatype triples. E.g., if the input document had the triple > ex:a ex:dp "1.00"^^xsd:decimal . > then after loading, the active graph could contain > ex:a ex:dp "1.0"^^xsd:decimal . > I guess. Is that right? > > The question is do we want to enforce something more specific? > > Birte > > > On 5 March 2010 10:07, Andy Seaborne <andy.seaborne@talis.com> wrote: > > The SPARQL query really starts where the data is already loaded (FROM etc > > not withstanding) so the data as it is loaded may be prepared in some > > fashion outside the SPARQL spec. > > > > When we discussed this last time, we recognized that systems already did > > work on loading RDF and did not introduce any text to obstruct them. > > > > As to whether it's an "entailment regime", if it is then it's finite and > > different for each system. It is done when data is loaded not queried > > (think running rules over the data). > > > > > > For example, TDB canonicalizes integers between -2^55 and +2^55-1 but not > > outside that range (they have their original lexical form stored). Decimals > > have 48 bits of precision and 8 bits of scale and again if outside the that > > range, the normal node storage is used and the lexical form is not > > canonicalised. > > > > Derived integer types are promoted to integer. > > > > (This in TDB is all "currently" and planned to change a little). > > > > Andy > > > > On 05/03/2010 9:29 AM, Polleres, Axel wrote: > >> > >> Thanks andy, my (maybe naïve) question would then be: is behavior 2 > >> warranted "as is" by the current spec, or is "canonical datatype > >> representation" actually another (commonly used already) "entailment regime" > >> that should be defined as such? > >> > >> Best, > >> Axel > >> > >> ----- Original Message ----- > >> From: Andy Seaborne<afs@talisplatform.com> > >> To: Polleres, Axel > >> Cc: ivan@w3.org<ivan@w3.org>; > >> public-rdf-dawg@w3.org<public-rdf-dawg@w3.org> > >> Sent: Fri Mar 05 09:06:09 2010 > >> Subject: D-enatilment and canonicalization > >> > >> > >> > >> On 05/03/2010 8:45 AM, Polleres, Axel wrote: > >>> > >>> In my opinion this is a question concerning all entailments from > >>> D-entailment "upwards". > >>> > >>> ----- Original Message ----- > >>> From: Ivan Herman<ivan@w3.org> > >>> To: Polleres, Axel > >>> Cc: Birte Glimm<birte.glimm@comlab.ox.ac.uk>; SPARQL Working > >>> Group<public-rdf-dawg@w3.org> > >>> Sent: Fri Mar 05 08:08:10 2010 > >>> Subject: Re: [TF-ENT] Condition C2 modifications > >>> > >>> > >>> > >>> On 2010-3-5 24:36 , Axel Polleres wrote: > >>>> > >>>> No objections, but one additional side question: > >>>> > >>>> Do we have an issue with systems that use canonical forms of datatype > >>>> literals internally? > >>>> > >>>> Say you have: > >>>> > >>>> :s :p "1.000"^^xsd:decimal > >>>> > >>>> is a Datatype-aware system really supposed to return > >>>> > >>>> "1.000"^^xsd:decimal > >>>> > >>>> on { :s :p ?O} > >>>> > >>>> but not it's internal representation? > >>>> > >>>> > >>> > >>> This is a good question, I do not know the answer:-(, but is this an > >>> entailment specific question? I would expect that to be a question for > >>> SPARQL as a whole... > >>> > >>> Cheers > >>> > >>> Ivan > >> > >> There are 2 cases for value aware systems and there are examples of > >> systems in each case: > >> > >> 1/ Data "1.00"^^xsd:decimal, > >> stores "1.00"^^xsd:decimal, > >> matches "1.0"^^xsd:decimal, > >> matches "1.00"^^xsd:decimal, > >> returns "1.00"^^xsd:decimal > >> > >> i.e. the original term is stored and returned > >> > >> 2/ Data "1.00"^^xsd:decimal, > >> stores "1.0"^^xsd:decimal, > >> matches "1.0"^^xsd:decimal > >> matches "1.00"^^xsd:decimal (canonicialization applied) > >> returns "1.0"^^xsd:decimal > >> > >> i.e. the canonicalized term is stored and returned > >> > >> > >> See also "1"^^xsd:byte and "1"^^xsd:integer > >> > >> I avoided describing them as D-entailment because that really is a set > >> of possibilities depending on the datatypes supported and ranges of > >> values within the datatypes. They don't necessarily force D-consistency. > >> > >> Andy > >> > >> Examples: > >> 1 - Jena memory model > >> 2 - Jena TDB > >> > >> ______________________________________________________________________ > >> This email has been scanned by the MessageLabs Email Security System. > >> For more information please visit http://www.messagelabs.com/email > >> ______________________________________________________________________ > > > > > > > > -- > Dr. Birte Glimm, Room 306 > Computing Laboratory > Parks Road > Oxford > OX1 3QD > United Kingdom > +44 (0)1865 283529 >
Received on Friday, 5 March 2010 13:34:34 UTC