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Re: Semantic languages and rules

From: <Joachim.Peer@unisg.ch>
Date: Tue, 18 Feb 2003 17:12:45 +0100
To: "Charlie Abela" <abcharl@keyworld.net>
Cc: www-rdf-logic@w3.org
Message-ID: <OF10B29C66.6FD163CC-ONC1256CD1.00559A16@unisg.ch>

Hi Charlie,

>So why is it
>necessary for DAML+OIL or OWL (being based on it, even though more
>expressive) to be augmented with rules?

the point is that Description Logics (like DAML+OIL/SHIQ or OWL) are just
*fragements* of first order logics, *forbiding or restricting * the use of
certain elements of logics  (which, in turn, enable more efficient
reasoning). The restrictions where designed in a way that they do not
really hurt the application area of Description Logics, that is, the
description of  things/domains. Now, as we are dealing with the application
area of Web Service Descriptions there is quite some information that we
would like to capture (for example complex rules for calculating the price
of a product, etc.) but that is not necessarily possible DL's restricted
set of logical constructs.

Among the restrictions are:
* to use only unary and binary predicates to describe the domain
* to define concepts using _one_ free variable, i.e. a concept definition
is a formula with one free var.

For a detailleddescription of the relationship between FOL, Horn Logics and
DL i recommend the following articles:

* Benjamin N. Grosof and Ian Horrocks: "Description Logic Programs:
Combining Logic Programs with Description Logic" By . Working Paper,
version of Nov. 21, 2002.
* Alon Y. Levy and Marie-Christine Rousset: "CARIN: A Representation
Language Combining Horn Rules and Description Logics", European Conference
on Artificial Intelligence, 1996
* Ulrike Sattler, Diego Calvanese, and Ralf Molitor : "Relationship with
other Formalisms", in: The Description Logic Handbook: Theory,
Implementation and Applications, 2003

>Where will these be introduced in TBL's semantic web layers?

AFAIK, people currently draw the layer cake as follows
xml < rdf m&s < rdf schema < ontology < rules < logic framework < proof <
[where "x < y" means y is built on top of x]

cheers and greeting to (i bet, sunny?) Malta :-)

Joachim Peer
Research Assistant
MCM Institute, University of St. Gallen
Blumenbergplatz 9, 9000 St. Gallen, Switzerland
Phone: ++41 (0) 71 224 3441, Fax: ++41 (0) 71 224 2771

                      "Charlie Abela"                                                                                                   
                      <abcharl@keyworld         An:      <www-rdf-logic@w3.org>                                                         
                      .net>                     Kopie:                                                                                  
                      Gesendet von:             Thema:   Semantic languages and rules                                                   
                      18.02.2003 16:28                                                                                                  

Hi all,

I have read the mailing thread RE: Action Items written by Pat Hayes and
dated 02/12/03 in the US/EU joint-committee archive. It sparked some
thoughts in my mind about some issues which a newbie like myself might take
as forgranted. I am presently doing some research on semantic web
applications in particular about semantic web services composition. From
what I have been reading about rules, rule markup, defintion of business
rules, use of rules for Ws composition, I am now feeling a bit confused
about all this.
Consider DAML+OIL, based on DL and capable of expressing knowledge in
machine interpretable format. With DAML+OIL one can specify a number of
facts from which inferencing of other facts can be made. So why is it
necessary for DAML+OIL or OWL (being based on it, even though more
expressive) to be augmented with rules? Where will these be introduced in
TBL's semantic web layers?
Also and this question might be more appropriate in the ws-mailing list:
important is the use of rules in defining ws composition, when one
the expressivity of languages such as DAML-S.
Can someone clarify in laymens terminology these issues. Or am I missing



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Received on Tuesday, 18 February 2003 11:12:09 UTC

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