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Re: More research on resources, think it's all here

From: Jonathan Borden <jonathan@openhealth.org>
Date: Fri, 20 Sep 2002 17:33:18 -0400
Message-ID: <000f01c260ed$566a5500$7c674544@ne.mediaone.net>
To: "Tim Bray" <tbray@textuality.com>, <www-tag@w3.org>

Tim Bray wrote:
>
> The latest draft of RDF Model Theory
> (http://www.w3.org/TR/2002/WD-rdf-mt-20020429/) says a couple of
> interesting things.
>
...>
> And in section 1.2 "Urirefs are treated as logical constants, i.e. as
> names which denote something (the things are called 'resources', but no
> assumptions are made about the nature of resources.)"
>

Perhaps the most definitive statements are found in: 0.2 Graph syntax
(http://www.w3.org/TR/rdf-mt/#graphsyntax) where:

[[
To describe RDF graphs it is first necessary to define the things that can
act as nodes and arcs of the graph. There are three kinds of node in any RDF
graph: urirefs, literals, and blank nodes. A uriref is defined to be a URI
reference in the sense of [RFC 2396]. An RDF literal has three parts ( a
bit, a character string, and a language tag), but we will treat them simply
as character strings, since the other parts of the literal play no role in
the model theory. Blank (unlabeled) nodes are considered to be drawn from
some set of 'anonymous' entities which have no label and are unique to the
graph. Finally, every arc in an RDF graph is labelled with a uriref. The
same uriref may label several arcs and also be a node in the graph. An RDF
graph can then be defined as a set of triples of the form <S, P, O>, where P
is a uriref, S is either a uriref or a blank node, and O is either a uriref,
a blank node, or a literal. It is convenient to adopt a familiar abuse of
terminology and identify a single triple with the graph consisting of the
singleton set containing that triple.

We refer to urirefs and literals (but not blank nodes) as names; but note
that there is no distinction between the name of a node and the node itself.
A name may occur in more than one graph, but blank nodes are unique to each
graph. This reflects the fact that literals always have the same meaning and
urirefs are considered to have a 'global' meaning but blank nodes do not.
(Note that this is a simplification from earlier versions, which
distinguished between literals and literal nodes.)
]]

In particular: _note that there is no distinction between the name of a node
and the node itself_

In terms of a URIref, if there is no distinction between the name (the
URIref) and the node (i.e. the resource) then the two are said to have
_identity_.

Jonathan
Received on Friday, 20 September 2002 17:50:58 GMT

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