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Re: live meaning and dead languages

From: rick <rick@rickmurphy.org>
Date: Mon, 09 Feb 2009 22:47:00 -0500
Message-ID: <4990F8B4.1060601@rickmurphy.org>
To: semantic-web@w3.org

See below ...

Richard Cyganiak wrote:
> On 8 Feb 2009, at 18:11, rick wrote:
>> As I have written before, the model theory on which the semantic web 
>> is based is defined in Alfred Tarski's Semantic Conception of Truth.
> Rick, that's overstating the role of model theory on the Semantic Web.

The statement above makes no reference to the ROLE of the model theory 
on the semantic web. But I'm glad you raised the issue. This statement 
asserts the model theory on which the RDF semantics are based. And the 
astute critic of the above would actually claim that I have understated 
the model theory by not citing Kripke and possible worlds.

> The formal semantics of RDF, as defined in [1], are based on model theory.

Yes, that's my assertion, too. Did you have something more specific to 
say about which model theory? Possibly LBase?

> But a lot of the deployed usage of RDF considers it simply as a 
> distributed graph data model, and ignores (or even violates) the model 
> theoretic semantics.

So this statement about the ROLE of model theory raises two important 

1. If one is ignorant of model theory, does that invalidate model theory?

2. If one violates the model theoretic semantics of the semantic web, is 
the deployed usage part of the semantic web?

In either case I think there answer is no.

First, consider music theory as an analogy. If I play two notes B and F 
simultaneously on my guitar that form a harmony called a tritone, but I 
am ignorant of the music theory of tritones, are these two notes any 
less a tritone? I believe my ignorance does nothing to invalidate music 

Second, the RDF semantics is a W3C recommendation which I understand is 
a normative document. In addition, the LBase Working Group Note defines 
LBase as the model theory of all semantic web languages. By definition, 
any language whose model theory is not LBase is not a semantic web language.

Would you suggest the recommendation and note be deprecated to suit the 
convenience of usage?

Again, my claim is that some arm chair philosophizin' would save the 
semantic web community some time. I'm not alone in this opinion, but I 
suggest that's a decision made by each individual that best suits their 
interests and abilities.

> Various non-RDF technologies, such as Topic Maps or microformats are 
> often lumped under the Semantic Web umbrella as well.

So is your claim that RDF technologies and non-RDF technologies that 
violate the RDF semantics are part of the semantic web? What then are 
the criteria for a semantic web technology? And how many other 
technologies are semantic web technologies?

> So, only a particular part of the Semantic Web technology portfolio is 
> based on model theory. I agree, however, that it's the part that can 
> benefit most from armchair philosophizing.

As above, I suspect there's some good debate in drawing the boundary 
around what's in this semantic web technology portfolio. Once the 
boundary's drawn and there's agreement on questions 1 and 2 above, let 
the philosophizin' begin.

> Have fun,
> Richard
> [1] http://www.w3.org/TR/rdf-mt/
>> Briefly, Tarski defines truth in terms of material adequacy and 
>> formal correctness. Note that Tarski does not define meaning, only 
>> truth. I think everyone would agree that material adequacy applies 
>> only to resources can be dereferenced and that  it is formal 
>> correctness that provides the foundation for inference.
>> So what can we say about meaning on the semantic web? We can say that 
>> URIs are definitions, but we need to be clear that meaning is not 
>> definition. Quine writes about this in Two Dogmas of Empiricism. Live 
>> meaning as referenced above implies interpretation.
>> The question then is whether inference is interpretation. I believe 
>> inference as used on the semantic web is necessary, but not 
>> sufficient for interpretation. Interpretation as it applies to 
>> meaning implies abduction as well as induction and deduction. 
>> Inference on the semantic web implies formal correctness and truth.
>> It's not clear whether the semantic web lacks this design principle 
>> intentionally, but without this design principle, the semantic web 
>> will lag the web in its utility.
>> As a compelling example, consider how the web serves as a meme pool 
>> for cultural transmission. How would we expect the semantic web to 
>> serve as a meme pool with dead languages ?
>>> I think this worry becomes more so as axioms and systems of axioms 
>>> become more complicated. (I just about see similarities between OWL2 
>>> and the Shorter Latin Primer I had at high school).
>>> A term which is too tightly nailed down in its relationship to other 
>>> terms has been dug into an early grave. Having fixed its meaning, as 
>>> our world moves on, the term will become useless.
>> A semiotic domain is a good next step to start developing this 
>> flexibility.
>>> The trick, in natural language, is that the meaning of terms is 
>>> somewhat loose, and moves with the times, while still having some 
>>> limits.
>>> This looseness of definition gives rise to some misunderstandings 
>>> (aka interoperability failures), but not too many, we hope.
>> Pragmatics is a step after semiotics.
>>> So I wonder, as some people try to describe some part of their world 
>>> with great precision, using the latest and greatest formal 
>>> techniques, just how long that way of describing the world will 
>>> last. Maybe there is a role in such precision in allowing us to be 
>>> clear about differences of opinion --- but it doesn't seem to me to 
>>> be a good foundation for building knowledge.
>> While I agree that we need to recognize the limitations of where we 
>> are today, I think Tarski's Semantic Conception of Truth is a pretty 
>> good place to start. We also need to recognize the challenges of 
>> moving along the path to live meaning.
>> If you're looking for some fun reading, Robert Kent has already 
>> defined the Information Flow Framework which parameterizes languages, 
>> logics, models and theories into a much more flexible approach than 
>> the semantic web. But hold onto your towel ...
>> http://www.ontologos.org/IFF/IFF.html
>>> Perhaps fortunately, I am an engineer not a philosopher!
>>> Jeremy
>>> [1] Don Cupitt, 2001, Emptiness and Brightness,  p95
>> -- 
>> Rick
>> cell: 703-201-9129
>> web:  http://www.rickmurphy.org
>> blog: http://phaneron.rickmurphy.org


cell: 703-201-9129
web:  http://www.rickmurphy.org
blog: http://phaneron.rickmurphy.org
Received on Tuesday, 10 February 2009 03:48:10 UTC

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