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Re: Datatype question

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 25 Jun 2002 14:25:16 +0300
To: ext Geoff Chappell <geoff@sover.net>, RDF Interest <www-rdf-interest@w3.org>
Message-ID: <B93E2DCC.17547%patrick.stickler@nokia.com>

On 2002-06-25 14:27, "ext Geoff Chappell" <geoff@sover.net> wrote:

> 
> ----- Original Message -----
> From: "Patrick Stickler" <patrick.stickler@nokia.com>
> To: "ext Geoff Chappell" <geoff@sover.net>; "RDF Interest"
> <www-rdf-interest@w3.org>
> Sent: Tuesday, June 25, 2002 6:33 AM
> Subject: Re: Datatype question
> 
> 
>> 
>> On 2002-06-25 13:22, "ext Geoff Chappell" <geoff@sover.net> wrote:
>> 
>>> ... My only point was that queries with
>>> multiple conditions are more efficient if those conditions have common
>>> bindings - e.g.  I'd rather be waiting for my system to process "{?a ?b
> ?c}
>>> and {?c ?d ?e}"  than "{?a ?b ?c} and {?d ?e ?f} and
>>> somefunc(?c)=somefunc(?d)".
>> 
>> Ideally, we should expect a datatype-capable RDF API to handle these
>> things for us, such that queries are made based on known values
>> rather than their literal denotation in the RDF graph. Such an API
>> would also equate the different local vs. global idioms accordingly,
>> such that
>> 
>>    Jenny age "010.00" .
>>    age rdfs:range xsd:decimal .
>> 
>> and
>> 
>>    Bob age [ xsd:decimal "10" ] .
>> 
>> would be comparable as
>> 
>>    Jenny age ?value .
>>    Bob age ?value .
>> 
> 
> I'd expect that would be the case for those datatypes that are natively
> supported by a particular system. For example you might rules like the
> following to allow such comparisons:
> 
> //inline case
> infer {?p ?s ?dv} from {[rdfs:range] ?p [xsd:decimal]} and {?p ?s ?o} and
> ?dv=dec(?o)
> 
> //qualified case
> infer {?p ?s ?dv} from {?p ?s ?o} and {[xsd:decimal] ?o ?v} and ?dv=dec(?v)
> 
> where dec is a function that returns a canonical decimal typed value given a
> string representation.
> 
> This would allow value comparisons without the combinatorial explosion I was
> worried about earlier (so what was my point, exactly? :-)

And the moment you start talking about <, >, etc. you're going to have
to use an RDF-external function anyway, so the benefit that tidy literals
seems to offer is really mostly an illusion in actual practice.

Cheers,

Patrick


--
               
Patrick Stickler              Phone: +358 50 483 9453
Senior Research Scientist     Fax:   +358 7180 35409
Nokia Research Center         Email: patrick.stickler@nokia.com
Received on Tuesday, 25 June 2002 07:20:49 GMT

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