From: Benjamin Grosof (bgrosof@MIT.EDU)
Date: 05/09/03
Hi folks,
I did a revised version of the document we discussed on the last JC telecon
-- the suggestions on roadmap for Rules with list of features, and thoughts
on their grouping and sequencing. Here it is.
The revisions were to add a few more features to the list -- things that
RuleML'ers have already been working on -- and
to incorporate a few suggestions wrt sequencing that came up in the
discussion on the last JC telecon.
Benjamin
% suggestions wrt roadmap for Rules in the Joint Committee
% by Benjamin Grosof
% created 5/6/03
% this version 5/9/03
Currently, we have two loosely-coupled efforts:
1. on Rules syntax and expressiveness, starting from RuleML
and (to a lesser degree so far) Common Logic as primary points of
departure
2. on use cases
Both involve analysis of requirements.
My suggestions for today address primarily (1.).
(2.) should definitely continue and be coordinated increasingly
closely with (1.).
I suggest several phases, to tackle various issues; see below.
I've probably forgotten to include some issues, and quite possibly
some more will arise during our design efforts. But I think
I've listed at least most of the issues.
Phase I: we start with defining:
o Datalog Horn logic programs, with URIrefs for predicate etc. logical
constants, cf. RuleML; and
coordinate/cross-fertilize this with the specification of
Datalog Horn FOL in Common Logic.
(Datalog here means without logical functions of non-zero arity.)
o then Horn without the Datalog restriction
o then extend with various additional features cf. RuleML's existing (V0.8)
or currently-in-discussion designs, again coordinating this with
the specification of Common Logic.
Phase II:
I've organized these into four groups (A,B,C,D below) of issues.
A reasonable sequence would be to tackle them in the following order.
But one could actually pursue them in nearly any sequence
(there are a few dependencies).
Group A:
Here are some additional features which apply in the pure-belief
logically-monotonic case, and thus also pertain straightforwardly
to Common Logic as well:
o modules: i.e., named rule subsets that can be imported.
This is a key Webizing feature.
o object-oriented argument collections: called "roli" in RuleML V0.8,
often called "slots" in KR literature
- related: lists, both ordered and unordered
o Lloyd-Topor And-Or: permit AND in the head; also permit OR (nestedly
with AND) in the body
o sorted/typed variables and constants: where the sort or type is
a pure predicate/class rather than (directly and more generally/impurely)
a programming language concrete type
o explicit equality predicate
o basic requests to perform inferencing
- query -- related to DQL;
there is a simple draft design of this in RuleML V0.8
- "trigger": request incremental or exhaustive forward inferencing
- permit new rulebase premises to be sent along with the query or trigger
o basic results of inferencing / justifications therein
- say that a rulebase entails a set of conclusions, or
that an engine/system/site inferred a set of conclusions from a rulebase
- called "turnstile" in previous RuleML design discussions
- related to DQL and DAML justifications efforts
o Lloyd-Topor more monotonic aspects: permit existential quantifiers
in the body, universal quantifiers in the head
Group B:
o rest of FOL in Common Logic:
notably quantifiers, classical negation, equivalences.
o This is not really rules in the LP sense, but is desirable to
coordinate with LP rules, and is technically related to the
Lloyd-Topor transformation feature of LP.
Group C:
Here are some additional features which involve non-monotonicity:
o negation-as-failure (NAF)
- this is particularly basic and urgent for practical rule systems
o Courteous / prioritized conflict handling / prioritized defaults
o selective closed-world-assumptions --
can often, or perhaps always, be defined as a special case of NAF or Courteous
o strong negation ("classical negation" in the limited sense used in
extensions of LP)
o full Lloyd-Topor transformation
o nonmon specification of equality theory over the Herbrand universe,
to generalize away from Unique Names Axiom;
e.g., via prioritized defaults about explicit equality predicate
Group D:
o standard pure-info built-ins; supporting libraries of built-ins,
e.g., standard ones for arithmetic, string, or list
comparisons or operations
- this is particularly basic and urgent for practical rule systems
o Situated / procedural attachments: NB: sensing includes an
important connection to querying and DQL
o Events handling
o evaluated functions: i.e., functions that are evaluated,
e.g., via built-in procedural attachments
- called "nano's" in previous RuleML design discussions
Group E:
o Transformation rules, in formal sense of what the rules produce
- nano's are related
- ask Harold for more explanation
Phase III:
An OWL meta-ontology of:
- expressive features above,
- and also of important/frequently-used restrictions, e.g.,
. stratified use of NAF,
. or predicates with arity of at most 2.
________________________________________________________________________________________________
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
This archive was generated by hypermail 2.1.4 : 05/09/03 EST