Re: Joint Committee telecon tomorrow 4 November

From: Ian Horrocks ([email protected])
Date: 11/05/03

  • Next message: Ian Horrocks: "Re: technical detail feedback on OWL Rules: truth value for empty consequent"
    On November 4, Benjamin Grosof writes:
    > At 05:26 PM 11/4/2003 -0600, pat hayes wrote:
    > >Suggestion, following Ben's reporting of Tim's observation. The ideas that 
    > >(1) an empty consequent is 'false' and (2) that a consequent is a 
    > >conjunction, are in opposition. The former arises historically from 
    > >thinking of a rule as an implication or a sequent, where a compound 
    > >consequent would be considered a disjunction.  I think this is a 
    > >fundamental snag in the current proposal ( sorry I didnt notice it before) 
    > >and suggest that we change the basic rule syntax slightly so that 
    > >consequents are atomic, not conjunctive, but then allow the present case 
    > >as a Lloyd-Topor style syntactic sugar for a conjunction of rules. This 
    > >changes the presentation slightly but makes it natural for an empty 
    > >consequent to be considered a missing atom - false - rather than an empty 
    > >conjunction - true. It also simplifies the semantics, and makes the 
    > >Lloyd-Topor mapping work properly in all cases.
    > this is fine by me as a way to define things.  6 of one, half dozen of 
    > another.  the main point is to make sure we explicitly define the case of 
    > empty head to mean false, rather than just say something like "the head is 
    > a possibly-empty conjunction of atoms".
    This is already the case, as you will see from the semantics:
    "A binding B(I) satisfies a consequent C iff C is not empty and B(I)
    satisfies every atom in C."
    > >Pat
    > >--
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    > ________________________________________________________________________________________________
    > Prof. Benjamin Grosof
    > Web Technologies for E-Commerce, Business Policies, E-Contracting, Rules, 
    > XML, Agents, Semantic Web Services
    > MIT Sloan School of Management, Information Technology group
    > or

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