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Re: D-enatilment and canonicalization

From: Axel Polleres <axel.polleres@deri.org>
Date: Fri, 5 Mar 2010 13:33:59 +0000
Cc: "Andy Seaborne" <andy.seaborne@talis.com>, <ivan@w3.org>, <public-rdf-dawg@w3.org>
Message-Id: <EF24C970-7C5E-4AF6-9B9E-1771A24CB8CB@deri.org>
To: Birte Glimm <birte.glimm@comlab.ox.ac.uk>

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 na´ve) 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
> >>
> >> ______________________________________________________________________
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> >
> >
> 
> 
> 
> --
> 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 GMT

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