# 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 UTC

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