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Re: [ontolog-forum] predicates in RDF

To: "[ontolog-forum] " <ontolog-forum@xxxxxxxxxxxxxxxx>
From: Chris Menzel <cmenzel@xxxxxxxx>
Date: Tue, 1 Jan 2008 11:44:42 -0600 (CST)
Message-id: <alpine.OSX.1.00.0801011101240.1532@xxxxxxxxxxxxxxx>
On Tue, 1 Jan 2008, paola.dimaio@xxxxxxxxx wrote:
> Coming from a linguistic background, I have always thought that
> predicate is a verb    (01)

Actually, the predicate of a sentence is usually identified with a verb
*phrase*, the part of the sentence that "makes the assertion about the
subject", as in your definition:    (02)

> CF. The predicate of a sentence is the part of the sentence that makes
> the assertion about the subject. The main part of the predicate is a
> finite verb (which must be present). The predicate can be a verb
> alone, or a verb and other words related to it. ...
> www.ntgreek.org/learn_nt_greek/terms.htm    (03)

Thus, e.g., the predicate of "John runs" is "runs" and the predicate of
"John loves Mary" is "loves Mary".    (04)

> but on the W3C spec, there is no such requirement/constraint
> http://www.w3.org/TR/rdf-concepts/#ref-rdf-semantics
> Is there no such implication that predicate must be a verb in rdf?    (05)

The question is ill-formed, as there is no such concept as "verb" in
RDF.  Indeed, there are no predicates per se in RDF, there are only
names (more specifically, URIs and literals) which denote "resources".
"predicate" itself just indicates a *role* that a name can play in an
RDF triple -- it is the name that "connects" the other two names in the
triple.  Any name can be the predicate in a triple.  That said, if an
RDF triple is used to represent a simple natural language sentence like
"John loves Mary" -- "<ex:j> <ex:l> <ex:m>", say -- the predicate in the
triple "<ex:l>" does in fact correspond to the verb in the sentence in
question.    (06)

The W3C RDF semantics document (authored chiefly by Pat Hayes)
http://www.w3.org/TR/2004/REC-rdf-mt-20040210 provides a very clear
account of these matters, though, it assumes some familiarity with basic
mathematical logic and set theory.    (07)

-chris    (08)

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