my notes from today's JC telecon

From: Benjamin Grosof (bgrosof@MIT.EDU)
Date: 06/03/03

  • Next message: pat hayes: "Re: DRAFT: List of Built-ins"
      (inline'd and attached too for convenience)
    % notes from JC telecon 6/3/03
    % by Benjamin Grosof
    Benj reviewed the basic definition of Horn LP
    can intro extensions which are reducible to the basic:
    - OR in body
    - existential in body
    - AND in head
    - universal in head
    Pat:  motivations for the definition and semantics?
    Gerd:  natural for executable to have a single intended [partial] model,
    similar to databases
    Pat:  Herbrand is useful for meta-theoretic and syntactic
    Benj:  has simplicity for implementation and also for specification
    Pat:  these questions will reemerge
    Mike:  e.g., how should it relate to semantics of RDF or OWL, as a target
    - Pat:  RDF is basically existential conjunctive logic
    - Benj: LP is actually much more established than DL or RDF or OWL
    - Mike: try to conform to OWL, head off any incompatibilities
    Pat:  differences between LP and OWL/RDF include:
    RDF and OWL all have classical model theories
    LP is fundamentally not monotonic and is recursive; it plays a different
    Gerd:  would not be as pessimistic as you
    Benj:  don't get hung up on the terminology of "model":
    the Horn LP conclusion set corresponds to the set of ground atoms
    that are entailed in Horn FOL
    Pat:  example:  RDF or OWL ontology that talks about colors,
    e.g., red, green, blue, that is integrated with PanTone (spelling?)
    which has URI's, and printing and a color-checking engine;
    in Horn LP model theory a name refers to itself, so can't
    express this well; will wreck things.
    Benj:  elaborate please?
    Pat:  point is that URI's have genuine denotations in the world
    Benj:  that's orthogonal to Herbrand-ness unless you can represent within
    the KR some info relating the denoter to the denotation
    Ian:  why stop at Horn LP rather than Horn FOL?
    Benj:  because it's well understood at a research level how to extend it to
    non-monotonicity and procedural attachments, but not to do so by extending FOL
    (tho' some procedural attachments can be handled in FOL).
    Also Horn LP is a waystation not a final destination -- it gets extended
    in two directions:  towards FOL/classical-logic and also towards
    fuller LP with nonmon and procedural attachments which is
    commonly used practically and relatively well understood theoretically.
    Gerd:  there is a generally used notion of rule systems, that is non-classical,
    e.g., has negation-as-failure
    Pat:  I'd like to get convinced that logic programs is the right notion that
    is widely used [in commercial rule systems] -- feel doubtful on this point
    general discussion on this point
    - Benj, Gerd, Said observing that
    Said:  policies
    Ian:  lots of these systems mix in programming application development
    features, don't they
    Said and Benj:  yes
    Benj:  but they're closer to declarative LP KR when you project onto
    their pure knowledge-based aspect
    important topics for future discussion:
    - built-ins (next week)
    - human-consumption string syntaxes (2 weeks from now)
    - explicit equality, names (3 weeks from now)
    - semantics of procedural attachments, how to relate that to classical logic
    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

    This archive was generated by hypermail 2.1.4 : 06/03/03 EST