OWL/RDF syntax for RuleML: my notes from discussion on JC telecon 4/22/2003

From: Benjamin Grosof (bgrosof@MIT.EDU)
Date: 04/24/03

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    Hi folks,
    Here are my notes from the discussion on our last telecon.  (Mike, you 
    might want to integrate some of this into your minutes.)
    % notes from Joint Committee discussion of abstract syntax for RuleML 4/22/03
    % by Benjamin Grosof
    % note the sequence below is reorganized (for clarity) from that of the
    % actual telecon discussion
    % the discussion revolved mostly around the more controversial aspect
    % of Benjamin's presentation:  should we try to provide an OWL or RDF syntax
    % for RuleML
    an objective favoring why try for an OWL syntax: represent the ontology
    of RuleML's sublanguages hierarchy, then use the same toolset
    for processing an instance rulebase
    another objective is to facilitate meta-reasoning about the rules
    themselves, e.g., to query for all rules whose head mentions a particular
    predicate P.
    another goal for why encode rules in RDF or OWL:
    conjecture that it will then be easier to extend RuleML to have more generic
    RDF or OWL for the arguments/terms within the rules
    Benjamin: in attempting an OWL syntax for RuleML, there are challenges of
    (1) closing-off, and (2) representing ordered collections in such a way that
    one can restrict the types of the members of the collection
    Benjamin and Stefan:
    one reason why aim for OWL rather than ,
    but still challenging in OWL currently, is the following
    objective: to enable XML-Schema's kind of validation, esp.:
    - check that a rulebase is well-formed syntactically
    - detect that a rulebase falls into a particular syntactic subset wrt
    which features are actually used
    Ora:  can view there being "conventions of usage" that go beyond what
    can be expressed in the OWL itself, e.g., wrt closing-off or orderedness
    Mike Dean and Peter and Pat:
    wrt challenge of how to represent ordered typed collections,
    e.g. lists of logical terms:
    can subclass off of rdf:list
    but then can't use parseTypeCollection to generate first, rest, end
    (? hope I understood this right)
    wild idea:  represent checking of that in RuleML itself
    one possible approach:
    define new RDF or OWL builtins for generic containers of typed members,
    then define subclasses and subproperties for specific usages,
    without changing fundamental DL expressiveness;
    e.g., indexed accessors for them, and a size/length/count property;
    e.g., a syntactic shorthand of _1, _2, ...;
    subproperty of ordered container index
    Peter:  also it's nice to detect "referential transparency",
    i.e., that every predicate mentioned actually has a (non-empty) definition
    Mike D. and Said and Benjamin:
    *in the rules requirements document, we should discuss the
    requirement that one can represent the ordering of rules within a rulebase,
    or the ordering of literals within a rule,
    since this is crucial for practical efficiency in many actual rule systems
    / engines
    - many others chimed in:  yes, that seems reasonable / important
    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
    http://ebusiness.mit.edu/bgrosof or http://www.mit.edu/~bgrosof

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