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Re: [ontolog-forum] is-part-of: a really, really, bad practice?

To: ontolog-forum@xxxxxxxxxxxxxxxx
From: John F Sowa <sowa@xxxxxxxxxxx>
Date: Tue, 21 May 2013 10:01:21 -0400
Message-id: <519B7E31.3040401@xxxxxxxxxxx>
On 5/20/2013 7:43 PM, jmcclure@xxxxxxxxxxxxxx wrote:
> *Tenseless Amodal Properties.* I'd like to know how you'd model
> this in RDF triples then
> past(Harry believes (John Know Bill))    (01)

RDF was designed for storing simple kinds of data in a database
that could be freely intermixed with other stuff in a web page.    (02)

The subset of logic represented in RDF has only two operators:
existence and conjunction.  Two or more triples in the same
page have implicit conjunctions among them.    (03)

A blank node is an implicit existential quantifier.  It says
that something exists that meets the criteria specified in its
triple (and the other triples in the same page).    (04)

As RDFS shows, it is possible to use RDF at the metalevel
to make certain kinds of logical statements.  The use of RDF
at the metalevel creates options for more expressive power.
But RDFS has the same logical limitations as RDF, and it
cannot compensate for the fundamental limitations of RDF.    (05)

> I know for me it'd be:
> Person:Harry had [[Belief:That JohnKnowsBill]]
> Belief:ThatJohnKnowsBill of [[Type:Belief]]
> Belief:ThatJohnKnowsBill of [[Type:Clause]]
> Belief:ThatJohnKnowsBill subject [[Person:John]]
> Belief:ThatJohnKnowsBill predicate [[Property:foaf:knows]]
> Belief:ThatJohnKnowsBill object [[Person:Bill]]    (06)

This is basically a translation of the syntax of a particular
English sentence (or the simple logic-like notation) to RDF.    (07)

To be a logic, you also need systematic ways of representing
the Boolean operators and quantifiers of that subset of logic,
rules of inference that determine what inferences are permitted,
and a model-theoretic semantics that can determine truth values
and can support proofs of soundness for the rules of inference.    (08)

If you want an epistemic logic (for knowledge and belief),
you need all of the above plus a lot more machinery for
representing whatever theory of knowledge you choose.    (09)

Summary:  If you want to represent logic, start by studying
logic in more general and more readable notations.  Then you
can decide what, if any, of that logic can or should be
mapped to a highly restricted syntax, such as RDF.    (010)

Even more importantly, ask yourself "Why?"  What benefits,
if any, would be gained by mapping that logic to RDF?    (011)

John    (012)

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