> Pat Hayes wrote:
>>> Hi Pat and all
>>>
>>> remind me please whatis CL for? what does it add to FOL or
>>> previous existing things?
>>
>> If FOL were a single formal language with a single, uniformly
>> accepted, universally used, syntax, then CL would add nothing. But
>> it isn't. Almost everyone who writes about FOL or uses it, uses a
>> slightly different notation. Everyone knows they are all
>> equivalent, and logically proficient users can switch (or even
>> muddle) notational conventions with impunity, and often do so; but
>> for information exchange between programs this is a nightmare. The
>> point of CL (and earlier, of KIF) was to provide a single standard
>> interchange notation for first-order logic.
>
> But as a model of a formal system, this approach falls short of what's
> already been defined by information flow, the information flow
> framework
> and category theory. (01)
Well, that's hardly surprising, given that CL never attempts to be a
"model of a formal system". Once again, CL defines a broad class of
(mostly first-order) languages + model theories (what I like to think
of as logics) and provides rigorous, standardized mechanisms for
translating information between them. (02)
>> The original intention was to adopt a single surface syntax upon
>> which everyone would agree: but when it became apparent that even
>> the ten or so members of the working group could not agree, this
>> idea was abandoned, and instead a system of a common 'abstract
>> syntax' allowing for many different 'surface syntaxes' (aka
>> dialects) was adopted. If you check the conformance conditions in
>> the ISO spec, they require that each dialect specification provide
>> a mechanizable process to parse that dialect into the abstract
>> syntax categories.
>>
>
> But thats only part of the answer (03)
To *what question*? CL a very complete answer to the question *we*
set out to answer. But there are tons of other questions and
challenges in knowledge engineering (vagueness, incomplete
information, poorly axiomatized knowledge bases, social/cultural
presuppositions, etc etc) that CL does not address. It strikes me
that your remarks are all about *those*. (04)
>> This should have been a simple exercise, but standardization
>> processes tend to run very slowly and often in circles, so this
>> limited goal took several years. Along the way, some of us (mostly
>> Chris Menzel and myself) noticed that traditional textbook
>> formulations of FOL contained a number of restrictions which were
>> not in fact strictly necessary, and almost as a exercise in pure
>> mathematics[1] set out out to see how far we could go in removing
>> them, and what effect this might have on the resulting logic. This
>> involved using a very neat mathematical trick which Chris showed to
>> me, of how to generalize the traditional FO model theory. Shortly
>> afterwards I became involved in the W3C RDF and OWL standardization
>> efforts, and realized that this same mathematical trick could be
>> applied to RDF and OWL, and would solve a number of small,
>> technical but stubborn problems that were plaguing the W3C working
>> groups, making RDF somewhat more intuitive (and simpler) than it
>> would otherwise be. So the RDF, and then the OWL, specs were
>> written using this same trick in their model theories, making the
>> entire family of languages (RDF, OWL, CL and now IKL) semantically
>> compatible in a rather strong sense. So this is another achievement
>> of the CL work, realized in CL and used very centrally in IKL and
>> OWL/RDF. But this is indeed rather a technical matter: it might be
>> compared to having an engine which uses a new fuel additive, where
>> the user of the logic is like the driver of the automobile. The
>> driver doesn't need to know how its done exactly, but the engine
>> responds better.
>>
>
> Is there a paper available on this? (05)
Several -- The RDF model theory (http://www.w3.org/TR/rdf-mt) and the
OWL model theory (specifcally the "RDF-Compatible Model Theoretic
Semantics": http://www.w3.org/TR/owl-semantics/rdfs.html) for
starters. Hopefully, the "freely released" status of the CL spec will
be approved soon. (06)
> So far it just sounds like abstraction which is ok on the way up,
> but leave you hanging on the way down. (07)
Well, uh, ok... (08)
-chris (09)
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