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Re: Requirement: queries written as RDF

From: Eric Prud'hommeaux <eric@w3.org>
Date: Thu, 1 Apr 2004 23:27:07 -0500
To: Rob Shearer <Rob.Shearer@networkinference.com>
Cc: public-rdf-dawg@w3.org
Message-ID: <20040402042707.GH15738@w3.org>

On Thu, Apr 01, 2004 at 12:30:46PM -0800, Rob Shearer wrote:
> I'd like some clarification of just what we're trying to get at from
> this requirement.
> Are we saying that we want queries to fit into the RDF/XML syntax? I'd
> like clarification on just what users and use cases benefit from such a
> syntax. My experience is that forcing RDF/XML syntax just makes it damn
> near impossible for humans to compose a document without lots of help
> from tools.

examples of queries in RDFXML:
  DQL: http://www.w3.org/2001/11/13-RDF-Query-Rules/#DQL
and other XML:
  XDD: http://www.w3.org/2001/11/13-RDF-Query-Rules/#XDD
  RuleML: http://www.w3.org/2001/11/13-RDF-Query-Rules/#RuleML
  QEL: http://www.w3.org/2001/11/13-RDF-Query-Rules/#QEL

>             If queries are being generated automatically, most software
> systems are pretty agnostic just what their output syntax is, so I don't
> see RDF representations as helping them much, either.

Such RDFXML query-generating tools would require a human-composable
query language to allow people to easily express their queries as
strings (unless we think everyone composing queries will use GUIs
and expert systems).

> Are we saying that we want queries to fit the RDF data model? If so, I
> don't think it's met trivially, since just about anything can be
> translated into RDF--that's the whole point of RDF.

Agreed. Once we know how to express a variable in the RDF model, I
think the query expression will fall out.

> Or are we saying that given some chunk of RDF, there should be some
> sensible query connotation that it invokes? Is this a roundabout way of
> getting back to entailment as an independent query--i.e. here's some
> RDF; does it necessarily follow from the source I'm querying?

I think we can express last option as a degernate form of a query with
a premise; the premise is written in RDFXML and the query is "is this
true?" If we treat it this way, we can also express premises for
queries in a more general case, ala "If prefectures and departements
are the same as states, what are the addresses of all the members of
the DAWG?"

 assume (jp:prefecture owl:sameAs fr:department &&
         fr:department owl:sameAs us:staet)
 ask (?who  wg:memberOf w3c:DAWG && 
      ?who  ad:workAddr ?addr && 
      ?addr ad:streetNo ?number && 
      ?addr ad:streetName ?street && 
      ?addr ad:city       ?city && 
      ?addr ad:state      ?state)
      ?addr ad:country    ?country)
 collect (?number ?street ?city ?state ?country)

Or maybe even negative premises: "If KendallC did NOT foaf:know DanC,
would he still transitively know PatHayes?"

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Received on Thursday, 1 April 2004 23:27:58 UTC

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