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RE: SPARQL question: get distinct list of datatypes used for literals

From: Seaborne, Andy <andy.seaborne@hp.com>
Date: Thu, 21 Aug 2008 21:14:04 +0000
To: Lee Feigenbaum <lee@thefigtrees.net>, "al@jku.at" <al@jku.at>
CC: Semantic Web <semantic-web@w3.org>, "public-rdf-dawg-comments@w3.org" <public-rdf-dawg-comments@w3.org>
Message-ID: <B6CF1054FDC8B845BF93A6645D19BEA34C42DE0631@GVW1118EXC.americas.hpqcorp.net>


> -----Original Message-----
> From: public-rdf-dawg-comments-request@w3.org [mailto:public-rdf-dawg-
> comments-request@w3.org] On Behalf Of Lee Feigenbaum
> Sent: 21 August 2008 18:26
> To: al@jku.at
> Cc: Semantic Web; public-rdf-dawg-comments@w3.org
> Subject: Re: SPARQL question: get distinct list of datatypes used for
> literals
>
>
> Andreas Langegger wrote:
>
> > Hi there,
> >
> > maybe sb can tell me if this is still possible: I'd like to fetch all
> > datatype URIs used for object literals in a dataset. There is the
> > dataset predicate which can be used in filter expressions to filter
> > literals to a known datatype like xsd:string: FILTER(datatype(?val) =
> > xsd:string).
> >
> > But can I bind the value to a variable somehow? With a filter it can't
> > work (consider FILTER(datatype(?val) = ?dt) where ?val is bound to
> > literal values and ?dt should give me the type). I could use property
> > functions, but I'd like to stay with SPARQL specs. Maybe there is a way
> > to do it I just can't see...
> >
> > thanks,
> > AndyL
>
> AndyL,
>
> There's no way to do this (select functions of values from a
> graph/dataset) in the SPARQL specification.
>
> As you said, various implementations provide extensions that will do
> this. Please see:
>
> http://esw.w3.org/topic/SPARQL/Extensions/Selecting_Expressions

>
> Lee
>
Yes - in strict SPARQL (simple entailment), a query can only return RDF terms found in the graph itself.


I'm sure someone can correct me, but D-entailment comes close: sec 5.1 of RDF sSemantics has the text:

"""
Say that an RDF graph recognizes a datatype URI reference aaa when the graph rdfs-entails a datatyping triple of the form

aaa rdf:type rdfs:Datatype .
"""

        Andy(S)
Received on Thursday, 21 August 2008 21:15:30 GMT

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