The contrast is between description-logic (DL) reasoning (of which OWL
is a variety) versus rule-based reasoning. Description-logic reasoning
gives you runtime class-subsumption checking and classification of
individuals based on necessary and sufficient definitions of classes.
Rule-based reasoning is not designed to do these tasks. On the other
hand, DL reasoning can't handle rules like (Father ?x ?y)(Brother ?x ?z)
=> (Uncle ?z ?y).
OWL has been augmented with a rule-language called SWRL.
DL reasoning typically makes open-world assumption. Jess uses
closed-world assumption.
Making sense of DL restrictions (e.g., class expressions) typically
requires the use of DL reasoner, which is difficult to simulate using
something like Jess.
Ontologies can be defined using DL language like OWL or frame-based
language (e.g., Protege frame). Protege frame also makes closed-world
assumption. Thus, JessTab works well integrating frame-based Protege
ontologies with Jess.
Samson
Martijn Tromm wrote:
Hi Gerhard,
I'm not very experienced with the technical of side of this, but I know
something about rules and ontologies. Rules can only work on some datamodel. An
ontology is nothing more than a formalized conceptualisation, so a extended
datamodel. Extended with what? Wel with, constraints, typing, hierarchies, and
rules. Expert systems can be seen as one of more possible implementations of
logic within applications. And when that logic is highly irregular and prone to
change than it is a good choice. OWL is one of more possible notations of
ontologies. w3c is busy with standards for OWL rules (very similar to RuleML I
believe). So rules and ontologies are a perfect couple. Expert systems shells
are terrific middle ware for dealing with the rules that will be formulated
upon ontologies. One of the big issues in this discussion is whether Owl
applications should be Closed World applications. (OWL is not closed by
default, but one can state a lot more rules under the CWA)
cheers,
Martijn
-----Oorspronkelijk bericht-----
Van: [EMAIL PROTECTED] namens Gerhard Austaller
Verzonden: vr 27-10-2006 23:10
Aan: [EMAIL PROTECTED]
Onderwerp: JESS: JESS vs RACER
Hi
I somehow completely lose overview on "semantic" technologies...
Does anybody know or is willing to explain where the
difference/overlap... between "expert systems" like JESS/CLIPS and
ontologies (with reasoners) is. Because of the rules it appears that
expert systems are more powerful but maybe there is something I can
express with ontologies that I can not within expert systems.
Another question is about RACER PRO. The query language NRQL looks like
a rule language in JESS. Is it RACER PRO's NRQL as powerful as the rules
in JESS? Maybe anybody knows both systems and could give a hint or a
link.
And last, does anybody know a way to import a OWL ontology into JESS.
Most solutions I know lose almost all restrictions. Is this an
implementation issue or is it because JESS (experts system in general)
are not to be used with "ontologies".
Thank you very much!
Gerhard
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Stanford University fax: 1-650-725-7944
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