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Some comments on RIF-BLD

From: Jan Maluszynski <janma@ida.liu.se>
Date: Mon, 22 Sep 2008 17:16:16 +0200
Message-Id: <200809221516.m8MFGHM5013624@portofix.ida.liu.se>
Cc: janma@ida.liu.se
To: public-rif-comments@w3.org

In my opinion the Working Draft on RIF-BLD of 30 July 2008
is a  mature  document and I would be glad to see  a Candidate
 Recommendation based on it. My interest on RIF-BLD is related
to my work on integration of rules and ontologies under the
well-founded semantics. 
(see e.g. Wlodzimierz Drabent, Jan Maluszynski: 
Well-Founded Semantics for Hybrid Rules. RR 2007:LNCS 4524,  1-15).

We are also working on rule languages
where uncertainty is handled in the framework of Rough Sets.
(see e.g. Jan Maluszynski, Andrzej Szalas, Aida Vitória:
 A Four-Valued Logic for Rough Set-Like Approximate Reasoning. 
T. Rough Sets 6: 176-190 (2007))

Some comments:

- Having more examples would be very helpful,

- The direct specification of RIF-BLD Semantics  (Section 3)  
follows closely the Semantic Framework of the Working Draft on RIF-FLD.
This is good,  but I would also expect to see  a  specialization of the
general framework to the specific case of RIF-BLD.
In particular, as RIF-BLD is claimed to correspond to the language
of definite Horn rules, the minimal Herbrand model semantics, should
perhaps be discussed. The minimal Herbrand model is   mentioned in
Section 3.8 of the RIF-FLD Working Draft as  an intended semantic
multi-structure of a RIF-BLD Sets of formulas,
but is not mentioned at all in the RIF-BLD working draft. 
Having clearly defined Herbrand models for RIF-BLD is
 important for the extensions where rule bodies include
negation-as-failure and for the approaches aiming on hybrid  integration
of such rules and ontologies (including our work based on the well-founded
semantics).

- The presentation syntax seems to be very useful. Having in addition 
 a variant of it using standard mathematical notation for quantifiers
 would be convenient in some cases, like teaching students with 
the mathematical background. Also, I wonder if the  universal 
quantification of rules must be explicit, in contrast to the standard
implicit quantification used in logic programming.

Jan Maluszynski
Department of Computer and Information Science 
Linköping University
581 83 Linköping
Sweden 
Received on Tuesday, 23 September 2008 08:22:49 GMT

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