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

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 SwedenReceived on Tuesday, 23 September 2008 08:22:49 UTC

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