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Re: Statements/Reified statements

From: Graham Klyne <GK@Dial.pipex.com>
Date: Thu, 23 Nov 2000 17:02:05 +0000
Message-Id: <4.3.2.7.2.20001123165324.00ad4480@pop.dial.pipex.com>
To: Jonas Liljegren <jonas@rit.se>
Cc: ML RDF-interest <www-rdf-interest@w3c.org>, Wraf development <rdf@uxn.nu>
At 04:47 PM 11/23/00 +0100, Jonas Liljegren wrote:

>Graham Klyne <GK@Dial.pipex.com> writes:
>
> > At 09:51 AM 11/23/00 +0100, Jonas Liljegren wrote:
> >
> > >This means that instead of four, we have five:
> > >
> > >{ uri, pred, subj, obj, model }
> >
> > I considered that approach for [1], but have preferred to use
> > properties to create the association between statement-resource and
> > context (model).  The above approach allows a given statement to be
> > associated with only one context/model, where properties allow a
> > given statement-resource to be incorporated into any number of
> > contexts/models.  That seems very much more in line with the RDF
> > philosophy of "anyone can say anything about anything".
>
>This depends on if you look at it as a statement or a stating.
>Anybody can state a specific statement but every stating is unique.

Well, I think that's a legitimate view.

My view (which I think is also legitimate ;-) is to treat the resource as a 
_model_ of the statement, and used as _part_ of a stating.  The actual 
stating is represented by the property that links the statement-resource to 
a context/model.

>There are three special cases:
>
>  1. Two URIs for the same statement:
>     S1: [A] --B--> [C]  (M1)
>     S2: [A] --B--> [C]  (M2)
>
>  2. The same URI for diffrent statements:
>     S1: [A] --B--> [C]  (M1)
>     S1: [D] --E--> [F]  (M2)
>
>  3. The same URI for the same statement:
>     S1: [A] --B--> [C]  (M1)
>     S1: [A] --B--> [C]  (M2)
>
>
>This means that neither the triple, nor the URI can be used as the
>unique key in the storage of RDF.  In the Wraf [2] DBI, I uses the
>kombination of model and URI as the key.

This is fine, and I think it's a perfectly valid implementation technique.

I think in terms of using a model of the statement that links the statement 
to a context as the primary key.  I think its another valid implementation 
technique.

What this debate tells me is that the minimalist RDF M&S approach to 
statements, triples and reifications is probably right, because a variety 
of implementation approaches can be mapped to it.  A model that dictated a 
particular implementation approach would probably not be a very good model.

[...]

>Am I right in thinking that you probably thinking that I make all this
>much more complicated than it ought to be? ;-)

No... I think you are quite properly considering the details of how you 
wish to implement an RDF processor, as I am doing.  What I do think is that 
one can and should separate what are "merely" implementation concerns from 
the fundamental properties of the underlying model.

#g

------------
Graham Klyne
(GK@ACM.ORG)
Received on Thursday, 23 November 2000 17:50:48 GMT

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