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Re: The place of rdfs:Literal's in the world...

From: <jos.deroo.jd@belgium.agfa.com>
Date: Mon, 29 Apr 2002 10:05:17 +0200
To: patrick.stickler@nokia.com
Cc: w3c-rdfcore-wg@w3.org
Message-Id: <OF6E5F0D0B.620B7876-ONC1256BAA.002AC09B@bayer-ag.com>


> I'd *really* appreciate some clarification on this issue. Thanks.

please check "RDF Model Theory Editors Draft 4/24/ 2002"
-> http://www.coginst.uwf.edu/~phayes/w3-rdf-mt-draft-42402.html


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.


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.)


(Intuitively, the vocabulary of a graph is the set of names that
need to be given an interpretation. We do not include literals in
the vocabulary because their interpretation is fixed.)


(the things are called 'resources', but no assumptions are made about
the nature of resources.) Literals are treated as denoting themselves,
ie each literal is essentially a quoted character string. (A further
proposal [@@ref datatype@@] supplies another vocabulary with semantic
restrictions which allow datatypes to associate values with literals.)


Turned around, this means that any assertion of a graph implicitly
asserts that all the names in the graph actually denote something in
the world. Similarly, the first rule implies that the universe must
contain every literal in the graph.


For example, a triple of the form

<ex:a> <rdf:type> <rdfs:Literal> .

is legal even though 'ex:a' is a uriref rather than a literal.
What it says is that I(ex:a) is a literal, ie that the uriref
'ex:a' denotes a literal.


Received on Monday, 29 April 2002 04:05:50 UTC

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