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Re: [ontolog-forum] Ontology-based database integration

To: "[ontolog-forum]" <ontolog-forum@xxxxxxxxxxxxxxxx>
From: "Len Yabloko" <lenya@xxxxxxxxxxxxx>
Date: Wed, 07 Oct 2009 18:50:24 +0000
Message-id: <W369002134778731254941424@webmail7>
Chris,     (01)

>On Wed, 2009-10-07 at 00:05 +0000, Len Yabloko wrote:
>> ...
>> Of course Semantic Web technologies are expanding now into these old
>> territories you have referenced with such detail and accuracy. But one
>> has to be very careful not to confuse semantic modeling with data
>> modeling and data linking with data integration. And, indeed, not to
>> confuse model-theoretic semantics (developed by Tarski for first order
>> logic and claimed by RDF) with various other semantics. 
>By saying RDF has "claimed" model theoretic semantics, do you mean
>anything more than that it has been provided with a model theoretic
>semantics?  That's a good thing, right?
>    (02)

Right. And I wish that fact was not given more significance than a small step 
forward in the right direction. By "claimed" I meant much broader claims made 
subsequently about RDF-based tool's potential to solve semantic 
interoperability problems.       (03)

>> I believe OWL itself is an attempt to go around the inherent
>> limitations of Semantic Web. 
>I'm not sure what limitations you have in mind.  OWL is an attempt to
>provide a standardized ontology language built upon a logical framework
>in which questions of consistency, validity, etc are decidable.  In
>general, such questions are not decidable, and that is certainly a
>limitation, but it predates the Semantic Web by several decades.
>    (04)

The limitations are well-known and recognized by creators of Semantic Web. 
Here is a good overview 
http://www.ibiblio.org/hhalpin/homepage/publications/html/airedux/    (05)

And yes - some of it predates SW. But there are many claims that SW somehow 
solves these problems, that somehow using SPARQL is solution to most of data 
integration needs.    (06)

>> I have been following these forum long enough to have heard all kinds
>> of claims about what is Semantics and many of these claims were tying
>> it directly to FOL, like no other logic or semantics ever existed.
>Really?  I can't remember anyone ever having made any such claim.  I
>frankly doubt whether you could find a single example.  What people
>*have* said is that, whatever representational medium you choose, it
>must have a clear model theoretic semantics (regardless of whether it
>happens to be that of classical first-order logic) so that the meanings
>of its primitive logical vocabulary and its basic grammatical constructs
>are well-defined.  Without that, questions of consistency and questions
>of whether one thing follows from another are, quite literally,
>    (07)

I don't want to get into this. Let's just say it was my impression.    (08)

>I believe this is what Ed had in mind when he wrote:
>> >Formal logic is a means of expression, in which the basic elements of
>> >the language have well-defined meanings and a set of well-defined
>> >manipulations retain those meanings, and nothing more.  
>I think by "well-defined manipulations" Ed means the inference rules of
>a logic -- whose legitimacy is justified by the underlying semantics.
>But, importantly, model theoretic semantics is very limited; it is
>restricted entirely to the assigning meanings to the basic logical
>expressions and telling us how to interpret the grammatical
>constructs of a language in terms of their simpler parts.  For
>nonlogical vocabulary, a model theoretic semantics tells us only the
>*kinds* of things signified by each grammatical category: e.g., names
>refer to individual things (whatever those are), predicates refer to
>classes, etc.  But *which* things the names of an ontology refer to and
>*which* classes its predicates pick out and exactly which classes a
>given individual belongs to and exactly what logical connections relate
>the classes we're interested in --- all of that is the job of what we
>might call "applied" semantics, a.k.a.  ontology. And model theoretic
>semantics is entirely silent on those questions.  As Ed put it:
>> >As to whether the snark actually is a boojum, classical formal logic
>> >offers only two possible interpretations:  it is either true or it is
>> >false, and it cannot be both.  And if you make a set of statements
>> >that allow the well-defined manipulations to produce a result of
>> >"true", then it does.  That's all there is; there ain't no more.
>> >Formal logic is about "how to think"; it is not about what you think
>> >about.
>That is pretty much spot on.
>Chris Menzel
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>    (09)

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