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Re: Statements/Reified statements

From: Graham Klyne <GK@Dial.pipex.com>
Date: Thu, 23 Nov 2000 11:05:58 +0000
Message-Id: <4.3.2.7.2.20001123105303.00bb32c0@pop.dial.pipex.com>
To: Gabe Beged-Dov <begeddov@jfinity.com>
Cc: ML RDF-interest <www-rdf-interest@w3c.org>
I agree with the broad thrust here, and I hope my other postings will 
reinforce that.  I have a couple of minor comments:

At 08:23 PM 11/22/00 -0800, Gabe Beged-Dov wrote:
> > Don't drop reification, it's heavy ;) I'd rather make it a lightweight
> > built-in feature by explicitly making every statement a resource.
>
>I hope others will weigh in here but it seems clear that there is a
>difference between the statement (member of Statements) and the
>reified statement in the model. This is used to distinguish between
>stating and quoting as others have said. It is explicitly part of the
>specification. How do you track quotings, i.e. the reification
>resource is explicitly present in the data source but the ground
>statement is not?

Yes.

>I empathize with the desire to make reification lightweight but I see
>replacing the triple with a quad (ReificationResource, subject,
>predicate, object) in the _implementation_ as being a good candidate
>for this. The quad represents the resource of type RDF:Statement (I'll
>just say RDF:Statement from hereon in as short-hand for the resource
>of type RDF:Statement) that needs to be generated for every statement
>that occurs in the source document (according to the spec).

Yes!!!

>There also needs to be a way to distinguish between the quoting
>RDF:Statements and stating RDF:Statements. I see two ways of doing
>this. One is to encode the information in the URI of the
>RDF:Statement. This will still not work in the case that the data
>source is explicitly creating both stating and quoting reification
>resources. The second way is to add information, either in-band in the
>model, or out of band in the implementation. I tend to prefer the
>in-band approach since it allows the information to standardized
>across implementations.

The idea of overloading URIs seems particularly evil.  I'm pleased you 
don't propose that.

As for adding the distinguishing information:  at one level, the 
distinction between a statement and a model (reification) of that statement 
seems to do just that.   At a different level, in my thoughts about using 
contexts for information modeling in RDF [1], I have found it useful to 
have "quotes" and "asserts" properties linking a statement-resource to a 
context.  (This is, I suppose, an extension of the RDF model as it is a 
mechanism for taking a reification and asserting the statement it 
models.  I am brewing some thoughts about RDF and sub-FOL logic 
capabilities but they've not yet come to the boil.)

#g

[1] (Work in progress) 
<http://public.research.mimesweeper.com/RDF/RDFContexts.html>


------------
Graham Klyne
(GK@ACM.ORG)
Received on Thursday, 23 November 2000 06:53:07 GMT

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