W3C home > Mailing lists > Public > www-rdf-interest@w3.org > November 2000

Re: A triple is not unique.

From: Jonathan Borden <jborden@mediaone.net>
Date: Mon, 20 Nov 2000 15:13:21 -0500
Message-ID: <028b01c0532e$56071680$0a2e249b@nemc.org>
To: "Dan Brickley" <Daniel.Brickley@bristol.ac.uk>
Cc: "McBride, Brian" <bwm@hplb.hpl.hp.com>, "RDF-IG" <www-rdf-interest@w3.org>
Dan Brickley wrote:

> hi
> On Mon, 20 Nov 2000, Jonathan Borden wrote:

> >
> > This is looking more and more like a gaping hole growing between the
> > and syntax parts of the specification.
> Perhaps. If forced to choose, I have little doubt that most implementors
> would take the model as primary. That said, I still lean towards the
> 'multiple statements per p/s/o' policy, since it fits best with most of
> the use cases I can think of for RDF reification.

    Perhaps we need to consider extending the RDF Model. My position is that
the model is unambiguous, but agree that it is perhaps too restrictive for
certain use cases. Again and again we run into problems related to a
monolithic model on a distributed web. If we introduce the concept of a
"space" to provide context to a set of statements, there would be no problem
with multiple statements having the same (p,s,o) as long as they "exist"
within distinct spaces.

    One way to formalize this is to state that:

There exists a set of spaces (sp)* contained by the global space g. A space
sp contains a set of statements (p,s,o)*. Spaces, predicates and subjects
are resources. An object may be either a resource or a literal string.

 This can also be formalized by considering a statement as a quad (sp,

> > 1) Just because it is syntactically possible to assign an rdf:Statement
> > ID doesn't mean that it ought be allowable to assign more than one ID to
> > same statement.
> How would you propose to police that? rdf:Statements will be manifested
> in thousands of RDF documents scattered around the Web. Does a statement
> gets its ID from the first (?!?) person to write it down in XML?

Unless we wish to change the RDF model, this is the predicament we would be
forced into, not terribly palatable.

 On the other hand, by the mechanism I propose above, as all statements are
predicated by a URI, each document might be partitioned into its own space.
We can easily define a syntax to aggregate documents into a containing
space. The term "context" can be substituted for the term "space".

Jonathan Borden
The Open Healthcare Group
Received on Monday, 20 November 2000 15:25:39 UTC

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