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RDF Concepts and Abstract Data Model: semantics

From: Jerome Euzenat <Jerome.Euzenat@inrialpes.fr>
Date: Wed, 4 Sep 2002 17:55:46 +0200
Message-Id: <a05111b07b99bc0ed3770@[194.199.20.189]>
To: www-rdf-comments@w3.org
Cc: Graham Klyne <GK@ninebynine.org>, "Jeremy Carroll" <jjc@hplb.hpl.hp.com>

Hi,

	about the "Resource Description Framework (RDF):Concepts and 
Abstract Data Model" document, I have comments about one minor part 
(viz. 2.3.1 Formal semantics):

| To serve this purpose, certain meanings of RDF statements must
| be defined in a very precise manner

why "certain" and which ones?

>Model-theoretic semantics assumes that a language refers to a 
>'world', and describes the minimal conditions that such world must 
>satisfy in order to assign an appropriate meaning for every 
>expression in the language.

"a language refers to a 'world'" is at least misleading:
- this is rather the assertions in the language which refer to the world.
- the word "a" here could lead the reader to equate one language or 
one set of assertion to one world, though the purpose of model theory 
is not to tie the assertion to one world but rather to consider all 
the possible worlds.

I offer the replacement:
"Model-theoric semantics defines the meaning of expressions in the 
language through a mapping (called interpretation) from a language to 
worlds. A set of assertions in the language, thus induce constraints 
on the acceptable interpretation (called model) of these assertions. 
The meaning of an expression is defined with regard to its 
interpretation in all the models."

I am sure that this is too technical, maybe reducing this part and 
refering to RDF-MT document is an easier alternative.

>  A particular world is called an interpretation, so that model 
>theory might be better called 'interpretation theory'.

Not accurate: an interpretation is a mapping from the language to the 
world. Indeed there can be many interpretations mapping to the same 
world.

A model of a set of assertions is an interpretation that satifies all 
the assertions in the set (i.e., which maps it to the element of a 
distinguished subset of the world for being very general, very often 
the set { true }). So model theory is well named.

Also in 3.5 RDF graph, in the Note:
- RDF Graphs are "node-labeled, edge-labeled directed multi-graphs" 
(with no disjointness constraints between node-labels and 
edge-labels): the multi- aspect is not in the note (i.e., that there 
can be several arcs between the two same nodes -- maybe with 
different labels).

Just for being nitty-gritty,
-- 
  Jérôme Euzenat                  __
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Received on Wednesday, 4 September 2002 11:57:27 GMT

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