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Re: RDFQ - RDF Queries in RDF

From: Patrick Stickler <patrick.stickler@nokia.com>
Date: Tue, 13 Apr 2004 10:56:38 +0300
Message-Id: <17BFA2CC-8D20-11D8-8853-000A95EAFCEA@nokia.com>
Cc: <public-rdf-dawg@w3.org>
To: =?ISO-8859-1?Q? "ext_Jean-Fran=E7ois_Baget" ?= <jean-francois.baget@inrialpes.fr>


This appears to sync well with what I've been doing with RDFQ and
URIQA concise bounded descriptions in our own environment (metadata
driven services/content for the Forum Nokia web site).

I certainly expect/hope that evaluation of queries expressed in RDF
would benefit from the RDF and OWL MTs where possible/appropriate.

Patrick


On Apr 08, 2004, at 17:38, ext Jean-François Baget wrote:

>
>
> Hi,
>
> Here are some notes and ideas about using RDFS and its semantics as the
> kernel of a query language. Intentionally, there is not much here on
> precise syntax for the language. Must it be all RDF/XML? The basic idea
> is that the kernel of the query must be an RDFS document, and that the
> answers to that basic query must be determined by RDFS semantics (or
> else, we don't work on top of RDFS...)
>
> Elementary query
> ----------------
>
> DATA:
> - The RDF Web (i.e. the set U = {D_1, ..., D_N} of all RDFS documents
> that can be found on the web)
> - The query
> 	- a RDFS document Q
> 	- A way to restrict U to one of its subsets (usefull for
> efficiency
> , thrust, ...)
>
> RESULT: A stream of answers
> An answer is:
> 	- A minimal subset A of the triples in the merge of U (or its
> obtained restriction) that is semantically valid and such that Q is a
> semantic consequence of A (in the sense of RDFS MT)
> 	- A way to check where do these triples in A come from (because
> thrust can be an issue)
> 	- Since entailment can be seen as a matching[*], the mapping
> from blanks in Q to terms of A (this is the proof of the entailment, 
> and
> the way to retrieve the result for an SQL-like query).
> 	
> [*] More precisely a graph homomorphism, the minimal subset is the
> homomorphic image, and the mapping the homomorphism itself.
>
> Building more complex queries
> -----------------------------
>
> Some things that we could do:
>
> FILTER THE STREAM OF ANSWERS
> Data: the answers stream
> By example by removing the answers where the image of a given blank in
> the query does not satisfy a given predicate.
> Result: a modified stream
>
> REORDER THE STREAM?
> In that case, should wait for its end...
>
> FORMAT THE STREAM OF ANSWERS
> 	- Extract the set of RDFS graphs from the stream (now we can
> compose queries)
> 	- Merge graphs
> 	- View the result as triples, graphs, tables,...
>
> ...
>
> Other ideas are welcome... Where to put disjunction, negation in this
> framework?
> 	
>
> Example: Find the email address of "John Smith"
> -----------------------------------------------
>
> The query is:
>
> _john foaf:name "John Smith".
> _john foaf:mbox _johnmail.
>
> The universe to explore is limited to the file where the user has its
> addresses.
>
> Hopefully the stream of answers returns a single answer[*]
>
> _x345 foaf:name "John Smith" .
> _x345 foaf:mbox john.smith@example.org .
>
> [*] May be an interesting feature would be to declare that a single
> answer (up to equivalence) is expected, otherwise a warning could be
> given.
>
> All triples come from the same source
>
> _john is mapped to _x345 and _johnmail is mapped to
> john.smith@example.org
>
> We extract _x345 (i.e. the thing it is mappeded to), and obtain the
> address.
>
>
> I should write that properly, and look at more significant (difficult)
> examples...
>
>
>
> Jean-François Baget
>
> INRIA Rhône-Alpes
> jean-francois.baget@inrialpes.fr
> Tel: 04 76 61 53 27
>
>
>
>

--

Patrick Stickler
Nokia, Finland
patrick.stickler@nokia.com
Received on Tuesday, 13 April 2004 03:58:34 GMT

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