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

From: Geoff Chappell <geoff@sover.net>
Date: Mon, 3 Nov 2003 18:56:28 -0500
To: "'Dan Brickley'" <danbri@w3.org>, <www-rdf-rules@w3.org>
Message-ID: <002d01c3a266$19b91630$bca272d8@gsclaptop>



> -----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. 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 Monday, 3 November 2003 18:56:35 UTC

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