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Re: plural vs singular properties (a proposal)

From: Frank Manola <fmanola@acm.org>
Date: Sat, 5 Jan 2008 12:35:36 -0500
Message-Id: <D7C2B667-5CBE-4E73-B3DA-4E10A7CAF0D0@acm.org>
Cc: SWIG <semantic-web@w3.org>
To: Garret Wilson <garret@globalmentor.com>

On Jan 5, 2008, at 11:56 AM, Garret Wilson wrote:

> Frank Manola wrote:
>>
>> Garret--
>>
>> Assuming I understand what you're talking about, this *isn't* a  
>> conflict with the relational model.  To flesh out your example a  
>> bit, suppose you have a paper, book, or article, and want to  
>> record subject descriptors.  Likely there would be multiple values  
>> for "subject", and your relation to represent that would be
>>
>> Subject(publicationID, value)
>>
>> with tuples like (12345 is the publication identifier): <12345,  
>> semantic web>, <12345, database>, etc.
>
> Oh, I think I see where we're thinking cross-ways.
>
> I was thinking of each resource as constituting a distinct relation.
>
> You're envisioning that a particular RDF graph has exactly *one*  
> relation, with each triple constituting a tuple in that relation,  
> correct?
>
> Garret


You're right that I'm thinking of only one relation, essentially the  
"triple" relation.  This view reflects the following from section 1.1  
of RDF Semantics:
"Readers who are familiar with conventional logical semantics may  
find it useful to think of RDF as a version of existential binary  
relational logic in which relations are first-class entities in the  
universe of quantification. Such a logic can be obtained by encoding  
the relational atom R(a,b) into a conventional logical syntax, using  
a notional three-place relation Triple(a,R,b); the basic semantics  
described here can be reconstructed from this intuition by defining  
the extension of y as the set {<x,z> : Triple(x,y,z)} and noting that  
this would be precisely the denotation of R in the conventional  
Tarskian model theory of the original form R(a,b) of the relational  
atom."

As this text notes, an equivalent way to think about it is that each  
RDF predicate is a distinct binary relation (in the relational model)  
having two columns, one containing the subject URI (the key column),  
and the other containing the RDF object value (literal or URI).  This  
is essentially the normalized version I described in my earlier message.

--Frank
Received on Saturday, 5 January 2008 17:35:47 GMT

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