Hi Adrian, (01)
That is a very good point, and being able to run some kind of sanity
check on a model would be a good QA step. However I don't think one
should limit the expressivity of the model in order to achieve that aim. (02)
This is something I intend to look into further when we have an OWL file
format version of our (OWL / ODM based) model. (03)
Mike (04)
Adrian Walker wrote:
> Hi Mike,
>
> Any reasonably complex chunk of formally stated business knowledge is
> prone to errors.
>
> If you cannot run it, you have no way of debugging it, other than
> staring at it or arguing about it. Eventually, you'll get tired of
> doing that and let it loose on the world, errors and all.
>
> Of course being able to run it still means human effort is needed, but
> much of that effort is offloaded onto the computer.
>
> Cheers, -- Adrian
>
> Internet Business Logic
> A Wiki and SOA Endpoint for Executable Open Vocabulary English Q/A
> over SQL and RDF
> Online at www.reengineeringllc.com <http://www.reengineeringllc.com>
> Shared use is free, and there are no advertisements
>
> Adrian Walker
> Reengineering
>
> On Sat, Jul 31, 2010 at 11:54 AM, Mike Bennett
> <mbennett@xxxxxxxxxxxxxxx <mailto:mbennett@xxxxxxxxxxxxxxx>> wrote:
>
> One thing I would add to that (taking it in a different direction), is
> that for some of the reasons that one might use OWL or Common Logic,
> decidability is not even an issue. This is in formally recording and
> defining business facts. Rather than having modelers design a logical
> model from whatever they grasp of the business reality (while their
> personal grasp of those facts remains undocumented), more firms should
> really be pushing for a formal record of the business knowledge
> against
> which designers design their stuff - this is part and parcel of
> ordinary
> mature development methodology. In this context, the semantic model is
> never going to be reasoned over or used as an application in its own
> right, it's simply the hitherto missing record of how the business
> sees
> the facts that the data will be about.
>
> To achieve that end, one simply needs a suitably formal way of
> expressing real things and real facts about those things, under a
> simple
> and explainable theory of meaning (such as set theory, for OWL).
> So this
> is a good reason to use OWL (or other CL languages) which has
> nothing to
> do with the considerations addressed here.
>
> Maybe I'm stating the obvious but I think it's worth keeping in mind.
>
> Mike
>
> sowa@xxxxxxxxxxx <mailto: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
> <http://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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>
> --
> Mike Bennett
> Director
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> 89 Worship Street
> London EC2A 2BF
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--
Mike Bennett
Director
Hypercube Ltd.
89 Worship Street
London EC2A 2BF
Tel: +44 (0) 20 7917 9522
Mob: +44 (0) 7721 420 730
www.hypercube.co.uk
Registered in England and Wales No. 2461068 (06)
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