notes from today's JC telecon: Rules Lite work items and expressiveness (inline'd and attached)

From: Benjamin Grosof ([email protected])
Date: 08/12/03

  • Next message: Sandro Hawke: "Re: notes from today's JC telecon: Rules Lite work items and expressiveness (inline'd and attached)"
    % notes from JC telecon 8/12/03
    % by Benjamin Grosof
    - introduction of new proposal by Peter and Ian
    - Rules Lite plans, including work items and volunteering
    Mike Dean
    Benjamin Grosof
    Peter Patel-Schneider
    Harold Boley
    Said Tabet
    Ian Horrocks
    Pat Hayes
    Sandro Hawke
    ? perhaps one or two others
    Peter walked thru the proposal very briefly
    Peter:   body and head are each a conjunctive query
    Peter:  adding Horn to DL will result in undecidability
    issue:  explicit inequality (i.e., differentFrom) in head goes beyond Horn;
    perhaps reducible if there is a complete theory of equality, but is there
    another issue:  only-if direction goes beyond Horn
    actually can express head equality given Horn plus DL expressiveness
    (some discussion around desirability/feasibility of decidability)
    some initial volunteering:
    examples and test cases:  Mike, Said, and maybe Deborah
    warning label:  Benj and Pat
    concrete syntax:  Harold and Said
    abstract syntax:  Benj ;
        would also like later help from someone who worked on OWL abstract syntax
    Benj:  in addition it seems important to soon resolve also the ff.:
    - expressiveness -- esp. what further expressive restrictions or additions
    perhaps can defer the ff. additional work items:
    requirements and objectives statement
    updated roadmap
    semantics -- is simple since is just FOL essentially
    running of test cases using various existing tools
    agenda for next week:  schedule of these work items
    summary of expressiveness issues, earlier discussed, that will need to
    be resolved: [Benj, after the telecon, extracting from telecon discussion]
    - Datalog restriction (probable)
    - RDF lists permitted, but probably restricted somewhat:
         . blank nodes -- avoid in head; perhaps also avoid in body
         . avoid KIF's over-ambitiousness (consensus)
    - avoid 0-ary predicates (probable)
    - limiting equality as predicate
         . in manner similar to OWL-DL (probable)
         . esp. in head
    - permit conjunction within head in rule syntax, using expressive reducibility
         . naming of rules might be a complication
    - naming of rules (perhaps defer beyond Rules Lite)
    - how tight is layering semantically on top of RDF or OWL
    - be able to handle distributed facts:  import'ing, module union'ing
       . Benj:  propose to defer this a bit, beyond the basic proposal
    propose to keep it really simple:
    - Datalog, no head b-nodes, no 0-ary predicates, no head equality,
    conjunction within head, do permit rule names, do permit simple RDF lists
    - but people should develop test cases if they're worried/irked by these
    Harold:  Datalog can be problematic for lists unless have b-nodes
    would like to do b-nodes; will develop some test cases;
    painful not to permit this
    Sandro and Benj:
    but that's head existential, and thus not Horn; and permitting just in body
    would probably be confusing to users
    can get quite a bit of expressive power probably if do include
    how about we permit head conjunction
    is there a way to impose some restrictions on head b-nodes
    that enables reducibility
    maybe the real issue is gensym capability, but can't create new names
    based on variables if are restricted to be Datalog
    Benj A to Pat Q:  the reason to stick to Horn as well-studied expressive class
    is that it has available:
    proof theory, completeness, algorithms, implementations
    that are tighter than full FOL
    Benj:  suggest the way to resolve this b-node issue is with some use cases
    - Mike; Sandro will help review
    agenda for next week:
    - IJCAI report from Ian
    - more on Peter and Ian's proposal
    - schedule of our work items
    - use cases on b-nodes
    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 : 08/12/03 EST