Ontologies are descriptions of types of entities and how they relate to
one another and the properties and capacities of the entities
themselves.  Essentially, they are about structure, properties and
capabilities.  In simulation models using JESS or other declarative
tools, the rules allow and constrain the development of process.  The
processes can be sequences of actions by instances described in an
ontology or they can change relationships and structures.  If the
relationships and structures do not change, then the ontology constrains
the declarative processes.  If the processes -- the behaviour of
individual entities and interactions among them -- change the structure
of the system, then the ontology and declarative processes co-evolve.

One would not expect to be able to import ontologies into JESS because
that would amount to importing the system structure into system
processes.  The two are by no means independent but neither are they the
same.

As for RACER in relation to JESS, again the functions are different.
RACER ensures that the ontology is sound and consistent relative to its
underlying logic.  JESS will have an underlying logic and programs that
do not crash will be sound and consistent relative to that logic.  As
far as I know, however, no one has identified the axioms and rules of
inference of that logic.  There have been declarative languages
implemented to be sound and consistent with respect to one or another
known modal logic.  In such cases we have the logic of the structure and
the logic of the processes.  I don't think they are likely to be the
same and I am not aware of any arguments that they should (or even
could) be.

Perhaps others on this list know better?

Scott

ps:  I don't think this is in conflict with Martijn's posting.


On Fri, 2006-10-27 at 23:10 +0200, Gerhard Austaller wrote:
> 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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