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RE: SeRQL an RDF rule language: scoping Rules vs Query in W3C wor k

From: Seaborne, Andy <Andy_Seaborne@hplb.hpl.hp.com>
Date: Tue, 4 Nov 2003 13:09:02 -0000
Message-ID: <E864E95CB35C1C46B72FEA0626A2E8081ACF8B@0-mail-br1.hpl.hp.com>
To: "'Geoff Chappell'" <geoff@sover.net>, www-rdf-rules@w3.org

-------- Original Message --------
> From: Geoff Chappell <mailto:geoff@sover.net>
> Date: 3 November 2003 23:57
> > -----Original Message-----
> > From: www-rdf-rules-request@w3.org
> [mailto:www-rdf-rules-request@w3.org]
> > On Behalf Of Dan Brickley
> > Sent: Monday, November 03, 2003 9:58 AM
> > To: sesame-devel@lists.sourceforge.net; www-rdf-rules@w3.org
> > Subject: SeRQL an RDF rule language: scoping Rules vs Query in W3C
> > work 
> > 
> > 
> > Hi
> > 
> [...]
> > In this light, do folks on these lists think it is sustainable to
> > maintain that there's an interesting distinction still to be made
> > between work on RDF 'query' languages vs 'rules' languages.
> It's probably hard to get away from the fact that the body of a rule
> will likely look like a query, but I can imagine there could be some
> differences at the edges. 


This seems to me to be the important point in structuring any query/rules
work.  If there is a a common way of describing the the matching part of the
query/rule then have different handling of the results (results sets, RDF
templates, RDF subgraph, rule consequences and probably more).

Ordering and group seem to be part of the handling the results.  A sensible
implementation would use the result requirements to optimize the matching
part but conceptually they are different stages.

> For example, w/RDF Gateway[1] I often find
> myself using decidedly closed-world type things in queries (aggregation
> functions, negation-as-failure) that I wouldn't usually use in a rule
> (since queries typically occur at the application/consumer edge of the
> sw there seems less risk of an unsound triple escaping into the wild as
> there might be with rules). And of course there's ordering/grouping of
> result-sets that's pretty meaningless in a rules context (assuming of
> course your queries are returning resultsets and not just graphs). So
> from my perspective, queries and rules share similar ways of specifying
> conditions for binding variables but do different things with the
> results.
> I can also imagine a scenario in which sw rules come out of the gate
> more constrained (e.g. owl-rules [2]) than you'd want in a query
> language (e.g. I'd want to be able to have a variable in the predicate
> position of triple in a query language). If that occurred it would be
> good to separate them.
> > Can folks here imagine a workable W3C RDF Query WG constrained not to
> > get into Rules WG territory, but to maximise compatibility with a
> > (future? parallel) Working Group on Rule languages for RDF? Or are the
> > two technology areas too close?
> I'd hate to see two different solutions to the same (or very similar)
> problem. Maybe that's not the inevitable outcome of two groups,
> though....
> > (I invite continuation of this thread on www-rdf-rules, am sending
> > this to Sesame list too initially) 
> > 
> > thanks for your thoughts on this,
> > 
> > Dan
> rgds,
> Geoff
> [1] http://www.intellidimension.com
> [2] http://www.cs.man.ac.uk/~horrocks/DAML/Rules/
Received on Tuesday, 4 November 2003 08:16:05 UTC

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