sowa@xxxxxxxxxxx wrote:
>
> Cameron, Ian, et al.,
>
>
>> Wouldn't Common Logic be the
>>
> "logical" choice if one were to
>
>> relinquish
>>
> decidability? It's an ISO standard and tools are gradually
>
> starting to appear.
>
>
>>> OWL and CycL are not really
>>>
> comparable, because OWL is based on a
>
>>> fragment of First
>>>
> Order Logic that is known to be decidable, for which
>
> provably correct reasoning algorithms are known and for which effective
>
>
>>> implementations based on said algorithms are available.
>>>
> OWL's expressive
>
>>> power could, of course, be easily (indeed
>>>
> arbitrarily) extended if one
>
>>> were prepared to compromise on
>>>
> some or all of these design constraints...
> I am on my way home from
> Malaysia, where three collocated conferences discussed these and other
> issues: MJCAI (Malaysia Joint Conference on AI), ICCS (International
> Conference on Conceptual Structures), and STAKE (Semantic Technology And
> Knowledge Engineering).
> One of the invited speakers, Boris Motik,
> wrote his PhD dissertation on DLs, and he is now teaching at Oxford. He
> made the observation that the desire to enforce decidable models led to
> many dubious compromises, such as the limitation to tree-structured
> models. Unfortunately, such models cannot represent any structures that
> contain cycles.
> One example would be a benzene ring. You can
> represent a structure with 6 carbon atoms, but you can't say that the
> sixth atom is connected to the first because that would create a cycle.
> Instead of describing just one fixed intended model, a typical OWL
> description would have a huge number of models. (There are ways of
> getting around such restrictions, but they involve jumping through lots of
> hoops with a large number of complex conditions to state something very
> simple.)
> As another example, Botik showed a simple OWL description
> of the human heart. Unfortunately, that description had an infinity of
> models. One model had exactly one left ventricle (which most people
> have). But other models could have any number of left ventricles. There
> was no way to limit the intended models to those that have just one left
> ventricle.
> As a solution, Botik proposed an extension to OWL that
> allowed arbitrary finite graphs, which could contain cycles. As a
> convenient notation for that extension, he drew diagrams that looked very
> much like simple (non-nested) conceptual graphs.
> OWL should
> be considered an open-ended family of languages, starting with OWL full,
> OWL lite, OWL DL, OWL 2.0, SWRL, OWL-Graph, etc., etc., etc.
> These
> versions of OWL have only two things in common: the three letters O-W-L
> in their name, and the fact that every one of them is a dialect of Common
> Logic.
> Since this thread is also addressing CycL, we should point
> out that CycL could also be considered a dialect of Common Logic. CycL
> and CL are very easily comparable to OWL: They are supersets of all the
> OWL versions and they can be used to relate each and every one of them.
> That is a very useful property.
> As for undecidability, it is an
> interesting theoretical property. But Lenat and other Cyclers have
> observed that in the 26 years of Cyc, undecidability has never caused any
> serious problems for any practical application.
> Occasionally, a
> collection of Cyc axioms might cause one of their inference engines to get
> hung up in a loop. That is also true of every major programming
> language. Java, C, Fortran, etc. are all undecidable, and nobody
> cares. Programmers use methods of structured programming and design
> patterns that enable them to predict when they have safe programs, and
> they have a very large number of guidelines for ways of avoiding the
> infinite loops.
> If anyone asks how many tools are available for
> Common Logic, the short answer is the sum total of all the tools written
> for any and every dialect of Common Logic. That includes all the Semantic
> Web languages, all the theorem provers used for
tptp.org, and huge numbers
> of experimental and commercial tools available today. Among other things,
> Common Logic has been used to define the semantics of the UML diagrams
> (check Google for fUML or formal UML). So all of the UML diagrams can be
> considered dialects of Common Logic, and all the UML tools can be
> considered CL tools.
> The advantage of CL is the ability to relate
> anything stated in any of those languages to any other language. Very few
> logics have that property.
> When I get back home, I'll send more info
> with references to the details.
> John
>
>
>
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