W3C home > Mailing lists > Public > w3c-rdfcore-wg@w3.org > October 2002

Re: No more labeled nodes

From: pat hayes <phayes@ai.uwf.edu>
Date: Wed, 30 Oct 2002 18:19:03 -0600
Message-Id: <p05111b37b9e626eec63f@[65.217.30.130]>
To: Dan Connolly <connolly@w3.org>
Cc: w3c-rdfcore-wg@w3.org

>On Wed, 2002-10-30 at 16:37, pat hayes wrote:
>[...]
>>  Then Dave can just delete "identified by".  Nodes *are* urirefs
>
>yes, please.
>
>
>Some details:
>
>>  --------
>>
>>  0.2 Graph syntax
>>
>>  .....
>>  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 an RDF graph: urirefs, blank nodes and literals. A uriref is
>>  defined to be a URI reference in the sense of [RFC 2396]. Blank
>
>to be an +absolute+ URI reference in the sense of...

OK, will fix

>
>>  (unlabeled) nodes are considered to be drawn from some set of
>>  'anonymous' syntactic entities which have no label and are unique to
>>  the graph. Two graphs which differ only by having different blank
>>  nodes are isomorphic;
>
>I think I know what you mean there, but it doesn't seem
>very precise. Hmm...

Right, that needs a bit of work.

>
>>  we will not bother to distinguish between
>>  isomorphic graphs. Literals come in several forms. Simple literals
>>  consist of a unicode character string plus an optional XML language
>>  tag;
>
>Please, no. Just like urirefs *are* labels, strings *are*
>literals, please. That is:
>
>	Simple literas are either unicode character strings
>	or unicode character strings paired with a
>	language tag.

OK, I can go with that.

>
>(language tags aren't novel to XML; they're an Internet-wide
>thing.)

Hmmm. So there could be non-XML lang tags? What happens if one of 
those is used on an XML literal?

>
>
>>  typed literals consist of a unicode character string paired with
>>  a uriref which indicates a datatype; and a special class of XML typed
>>  literals is distinguished which can also have an XML lang tag.
>>  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 formally 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.
>[... very nicely put...]

Well, I think those were your words at the end there, in fact.

Pat



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Received on Wednesday, 30 October 2002 19:19:49 EST

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