Wanted: Test Case for Herbrand Semantics

From: Sandro Hawke (sandro@w3.org)
Date: 06/04/03

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    I think I heard two complaints about Benjamin's proposed style of
    rules-language semantics:
       1.  It's different from RDF and OWL, and that difference itself
           makes things more complicated.   Such a difference needs to 
           be well-motivated.
       2.  It's wrong, because it means you can't express knowledge about
           real things, like specific colors. 
    I would like to see a test case for #2.  Pat sketched one using
    colors, but I couldn't quite see the details.  Let me try another one
    using Said's example of financial regulations being published as
    As I recall from the bubble days, the American SEC has a rule saying
    that company founders cannot sell any stock within 6 months after the
    company goes public.    Perhaps they could publish a rule which
    various consumers could incorporate into their stock-trade planning
        sec:forbiddenTrade(?x) <-
           sec:seller(?x, ?person) /\
           sec:company(?x, ?company) /\
           sec:date(?x, ?saledate) /\
           sec:founder(?person, ?company) /\    
           sec:ipoDate(?company, ?ipodate) /\
           % ?saledate < ?ipodate+6 months; requires some date handling
    Let's look at that "sec:founder" predicate.  In RDF's semantics I
    would say it relates a person and a company.  In HornLP semantics, I
    would say it relates a term which presents a person and a term which
    represents a company.  Is that right?  Now the question is: how do we
    get the difference to show up?  Where does it matter?
    Benjamin's notes on the subject say:
    > Benj:  that's orthogonal to Herbrand-ness unless you can represent within
    > the KR some info relating the denoter to the denotation
    but I can't see how to get to that situation where it stops being
         -- sandro

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