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RE: BRQL and typed literals

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Tue, 27 Jul 2004 12:05:03 +0100
Message-ID: <E864E95CB35C1C46B72FEA0626A2E80803984CE8@0-mail-br1.hpl.hp.com>
To: Patrick.Stickler@nokia.com, "Seaborne, Andy" <andy.seaborne@hp.com>, public-rdf-dawg@w3.org

-------- Original Message --------
> From: Patrick.Stickler@nokia.com <mailto:Patrick.Stickler@nokia.com>
> Date: 27 July 2004 11:59
> > -----Original Message-----
> > From: Stickler Patrick (Nokia-TP-MSW/Tampere)
> > Sent: 27 July, 2004 13:49
> > To: 'ext Seaborne, Andy'; public-rdf-dawg@w3.org
> > Subject: RE: BRQL and typed literals
> > 
> > 
> > 
> > > 2. Simply adopt the standard N-Triples notation for typed literals
> >    including support for qnames (e.g. "10"^^xsd:integer). If a given
> >    query engine/service supports the datatype in question, fine, else
> > it issues an error. 
> > 
> Or alternately (and I've covered this in detail before, but
> thought to stress this point) the engine can opt to treat unknown
> datatypes such that, if the typed literal in a query matches
> exactly a typed literal in the knowledge base (both lexical form
> and datatype URI) then it can deem them to be equal and a match,
> otherwise it can treat it as a non-match (even if in fact
> they are equal values (e.g. "010"^^xsd:int and "10"^^xsd.int)
> and even issue a warning that some "real" targets may not have
> been found due to lack of support for the datatype in question.
> Thus
>    DESCRIBE ?x WHERE (?x ex:booga "xyz"^^foo:blargh)
> would still be a useful query, even for query engines who have no
> clue what the datatype foo:blargh is, because it can still find
> all triples explicitly matching that typed literal.
> Patrick

Actually, that syntax for literals is already in the strawman and is in most
RDQL implementations as far as I know.  There are shortcuts for xsd:integer
and xsd:double.

As to operations in such values, the WG has accepted it will identify a
subset of XML schema datatypes and operations. (That's 3.7) so there is a
common base that can be assumed to be there (implementations to date have
provided integer comparison, for example) and extensions, with the suggested
approach by function call (see the strawman doc) or by evaluating predicates
(c.f. cwm or iTQL).

Much detail to sort out, of course, especially the matters of value
comparisions you mention and the implications on databases.

Received on Tuesday, 27 July 2004 07:05:46 UTC

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