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Re: plural vs singular properties (a proposal)

From: Garret Wilson <garret@globalmentor.com>
Date: Sat, 05 Jan 2008 13:08:13 -0800
Message-ID: <477FF1BD.9020805@globalmentor.com>
To: Frank Manola <fmanola@acm.org>
CC: SWIG <semantic-web@w3.org>

Frank Manola wrote:
>
> I don't think it's as straightforward as you think to take Date's 
> comments about one notation for relations and apply them to another 
> (RDF).  See below.
>
...
>
> Now, while the representation is different, I would claim that the 
> semantics (the intended meaning) of these are the same.  You would 
> simply have to have agreement with those you're communicating with as 
> to how to interpret one of these representations as the more abstract 
> relational interpretation that Date is talking about.

That's an understandable and not unreasonable view of the situation. It 
seems to have several implications:

1. The relational model, then, is a rigorously defined data storage 
framework that may reflect semantics, but the semantics it reflects 
depend on external agreements by two communicating parties. (i.e. Using 
the a relation header to mean "predicate" is one interpretation among many.)

2. The RDF model is different from the relational model in this regard; 
it is a rigorously defined data storage framework the semantics of which 
are unambiguously defined by the framework itself, not by agreement 
between two communicating parties. (Of course, two communicating parties 
may add *additional* semantics.)

(Surely one must say that <rdf:Description rdf:about="#mybook" 
dc:title="My Book"/> has only one interpretation, namely, that some 
resource identified by <#mybook> has a dc:title of "My Book". That the 
semantics of dc:title is supplied outside the framework is beside the 
point here---that applies equally to Date's example and to mine.)

3. The semantics of the relational model when "interpreted in an obvious 
way" by Date in his wine example is an interpretation incompatible with 
and therefore unsuitable for representing RDF because it does not allow 
each predicate to be duplicated in the relation header.

>> Whew---did I get all that correct?
>
> I don't think so!  As I said earlier, I think the "equivalent 
> relational semantics" involve an interpretation of some explicit 
> notation for relational tables similar to that involved in 
> interpreting the RDF triples.

I didn't understand the part about "similar to that involved in 
interpreting the RDF triples", because as I understand it (see #2 above) 
RDF triples have only one interpretation, that of 
subject/predicate/object. (The issue of the actual semantics of a 
particular predicate is a different issue; with a relation, there are 
several way to represent a predicate without knowing what it means, but 
in RDF there is only one way to represent a predicate.)

Garret
Received on Saturday, 5 January 2008 21:10:03 GMT

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