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Re: Resolution of: #rdfms-identity-anon-resources

From: Sergey Melnik <melnik@db.stanford.edu>
Date: Fri, 12 Oct 2001 10:51:24 -0700
Message-ID: <3BC72D9B.4843BDD0@db.stanford.edu>
To: Graham Klyne <GK@NineByNine.org>
CC: RDF core WG <w3c-rdfcore-wg@w3.org>, Dave Beckett <dave.beckett@bristol.ac.uk>
It looks like it is still the case that RDF/XML syntax can only
represent a subset of valid RDF graphs, in which there are no circles
that contain bNodes only. If so, this limitation needs to be stressed in
the spec(s). An exception handling mechanism must be specified as well.


Graham Klyne wrote:
> [Re-post, with comments to specific issues raised in the original issue --
> see end of this message.  I've also re-phrased point 3 to avoid the phrase
> "normal use".]
> With respect to the issue:
> [1] http://www.w3.org/2000/03/rdf-tracking/#rdfms-identity-anon-resources
> Being a revision of my previous message:
> [2] http://lists.w3.org/Archives/Public/w3c-rdfcore-wg/2001Aug/0030.html
> And citing the model theory document:
> [3] http://www.w3.org/TR/2001/WD-rdf-mt-20010925/
> I propose the following resolution text:
> [[[
> 1. Resources that are described but not named in an XML serialization (by
> rdf:ID or rdf:about) are represented in an RDF abstract graph by nodes that
> do not have any associated URI.  Such nodes, called bNodes (from blank
> nodes) are thereby distinguishable from other described resource nodes,
> which do have an associated URI-reference label.
> To directly address the question of the issue:  a so-called anonymous
> resource has no URI.
> 2. To reflect un-named descriptions in N-triples, local names must be
> introduced (i.e. of the form '_:name').  These names are not URIs, and
> their scope is the N-triples document in which they appear.
> 3. In the defined use of RDF to express ground facts, the meaning of bNode
> is to assert the existence of at least one resource which is the subject
> and/or object of properties as indicated by the graph.  This is covered
> more formally by the Model Theory [3], section 2.  See also the anonymity
> lemmas in section 3.2.
> NOTE:  it has been proposed that the RDF graph syntax can be used for form
> a query, in which bNodes may be interpreted as query variables.  This
> resolution confirms that bNodes can be distinguished from other labelled
> nodes within the graph syntax, but is silent about if and how the graph
> syntax might be used to represent a query.
> This resolves specific questions in the original issue raised thus:
> [1.] Should anonymous resources have URI's?
> -- No (point 1 above).
> [2.] If so, should they be clearly distinguishable as parser generated URI's?
> -- Not applicable:  the parser is not required to generate URIs.
> [3.] Should there be a standard algorithm for generating URI's which ensures
>   that different parsers generate the same URI's from the same source
>   input document?
> -- No:  the parser is not required to generate URIs.
> [4.] How might these automatically generated URI's be affected by changes
>   in the source document?
> -- There no automatically generated URIs to be affected.
> ]]]
> #g
> ------------
> Graham Klyne

E-Mail:      melnik@db.stanford.edu (Sergey Melnik)
WWW:         http://www-db.stanford.edu/~melnik
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Received on Friday, 12 October 2001 13:25:47 UTC

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