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Re: To embed or combine

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Mon, 10 Sep 2007 09:07:57 +0200
Message-ID: <46E4ED4D.4060204@inf.unibz.it>
To: Chris Welty <cawelty@gmail.com>
CC: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

> <chair>
> The status of the discussion regarding Jos' RDF compatibility section
> appears to be mired in whether the normative semantics of RDF in RIF
> should be specified in the model theory through a "combination" of RIF
> and RDF semantics, or through an "embedding" of RDF semantics in RIF (as
> rules).  The two approaches have been shown by Jos to be equivalent.

The two approaches are only equivalent with respect to entailment. If
you want to extend either language (RDF for RIF), then they will differ.

> At the moment I have not seen any technical arguments supporting one
> approach or the other. 

There are two main technical arguments for the model-theoretic approach:

i) It directly extends the RDF (as well as the RIF) model theoretic
semantics, and is thus *by definition* faithful to the semantics.

ii) The approach is extensible, in the sense that it can be immediately
used for any semantic extension of RIF (or RDF, for that matter), such
as counting. The embedding of RDF in RIF would have to be reevaluated
for most kinds of extensions of RIF, in order to make sure the
entailments are the ones you might expect.

Best, Jos

> Michael prefers the "embedding" on the basis that:
> (1) the "combination" is more complicated than the "embedding" and thus
> more difficult to understand.
> (2) it is not our job viz. our charter to specify a model theoretic
> approach to the RDF/RIF combination
> Jos seems to prefer the "combination" and argues re: (1) that:
> (3) it is no more difficult to understand the "combination" than the RIF
> model theory.
> As chair, my own read of the charter does not provide any particular
> help on (2), I'm not quite sure what Michael is referring to there.  It
> is certainly our job to specify how RIF and RDF should be used together,
> and as chair I interpret this as meaning we should have a normative
> standard for that.
> Thus, as suggested by Michael, it seems to me we are at a difference in
> preference only, and I see no alternative other than to call a vote.  It
> seems to me the vote is about which approaches to make *normative*:
> 1) The model-theoretic "combination" of RIF and RDF is normative
> 2) The "embedding" of RDF semantics as RIF rules is normative
> 3) Both the "combination" and "embedding" are normative (What would that
> mean?)
> </chair>
> -Chris

Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
The third-rate mind is only happy when it is
thinking with the majority. The second-rate
mind is only happy when it is thinking with
the minority. The first-rate mind is only
happy when it is thinking.
  - AA Milne

Received on Monday, 10 September 2007 07:08:11 UTC

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