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Re: here's a draft charter strawman slideset, wrt W3C Rules WG

From: Jos de Bruijn <jos.debruijn@deri.org>
Date: Wed, 29 Jun 2005 10:10:09 +0200
Message-ID: <42C25761.1050908@deri.org>
To: Francois Bry <bry@ifi.lmu.de>
CC: public-rule-workshop-discuss@w3.org

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Francois Bry wrote:

> Benjamin and his friends did a siginificant work in drafting these
> principles!
>
> I have two provisos:
>
> 1. It would be agreable to receive files in a non-proprietary
> standard, eg. in a W3C standard. Those MS specific standards are
> alomst impossble to properly view on non-MS software, and I find it
> boring an inappropriate to have to start Windows for reading
> contributrions.

I could not agree more :)

>
> 2. I do not clearly recognise the central issue "What rules
> languiages what for". "Rules" means many different things that , I
> beleive, are better kept distinct:
>
> 2.1 views, or predefined queries (rfegardless of whether they are
> evaluated by forward of bac kwartd chaining, I fully agree with the
> proposal in this respect).
>
> 2.2 Integrity constraint-like rules, i.e. FOL-like or Description
> Logic-like, eg OWL, formuylas evaluated against a repository of
> factual data (eg database).
>
> 2.3. Ontology-like rules, i.e. FOL- or Description LOic-likre, eg
> OWL formulas considered independently of any repository of factual
> data.

I would say 2.3 incorporates both 2.1 and 2.2. OWL incorporates both
derivation rules (e.g. subclass axioms) and integrity rules (e..g.
disjointness axioms).
Because OWL is FOL-like, no factual data is required to reason over
the ontology and thus things like subsumption can be computed. But
this has more to do with the kind of semantics you use for the rules,
than the kind of rules you use.

>
> 2.4 active/reactive rules.
>
>
>
> More on the various kinds of rules:
>
> 2.1 and 2.2 (since integrity constraints are perfectly realized as
> special views) pertain to Query Languages. Therefore, any activity
> on a W3C rule language for the SW should be tightly joined with
> activities on SW Query language(s).

Completely agree. Rules and queries have always been closely related.
Typically, a query is a rule without a head.

>
> 2.3 is already investigated: OWL. The issue are thus (a) how to
> relate ontologies to views/integrity constraints, and (b) how to use
> a *same* formula either as integrity constraint (as explained above
> under 2.2) or as an ontology formula (2.3), as fare asw Negation is
> concerned cf Thesis 2 in http://www.w3.org/2004/12/rules-ws/paper/15/ .

There has already been a lot of discussion on how to integrate OWL and
rules. The two leading (well-known) ways to integrate them are:
- - use of a common subset; disadvantage is that many (especially DL
advocates) believe that this subset is too small for any useful ontology
- - exchange of consequences between the OWL KB and the rule base (e.g.
dl-programs by Eiter et al.)

As I already said, OWL contains integrity constraints. However, they
don't necessarily behave as you might expect, since they are not used
to check the integrity of the data, but rather to constrain the number
of first-order models.
It would, IMHO, be interested to see how we could relate OWL
(open-world) constraints, which are very helpful when reasoning over
the schema, and closed-world (and UNA) integrity constraints which can
be used to check a set of data. However, I don't think this should be
the focus of the WG.

>
> 2.4 Active/reactive rules can *not* be tackled on the distributed
> Semantic Web as elswewhere. New research is urgently needed, cf
> .e.g. the (draft) paper attached to this message (in PDF, not in a
> proprietary format! :-). There, a fully novel approach to reactivity
> wuth a kind of Event-Condition-Action rules tuned to the Web is
> proposed. Notice how this approach is copuled with a Web/Semantic
> Web query language, so as to achieve the interoperability needed by
> programmers. Feedback is very welcome!

IMO, active/reactive rules should not (yet) be the focus of the WG. I
think we should first tackle the problem of derivation and integrity
rules.


Best, Jos


- --
Jos de Bruijn, http://www.uibk.ac.at/~c703239/
+43 512 507 6475         jos.debruijn@deri.org

DERI                      http://www.deri.org/
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Received on Wednesday, 29 June 2005 08:10:19 GMT

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