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Re: [Editorial] "blank nodes do not denote specific resources"

From: David Booth <david@dbooth.org>
Date: Thu, 19 Jul 2012 09:39:45 -0400
To: Eric Prud'hommeaux <eric@w3.org>
Cc: Nathan <nathan@webr3.org>, public-rdf-comments <public-rdf-comments@w3.org>
Message-ID: <1342705185.3486.9156.camel@dbooth-laptop>
On Thu, 2012-07-19 at 07:13 -0400, Eric Prud'hommeaux wrote:
> * Nathan <nathan@webr3.org> [2012-07-18 22:24+0100]
> > David Booth wrote:
> > >On Wed, 2012-07-18 at 14:02 -0400, David Booth wrote:
> > >>http://www.w3.org/TR/rdf11-concepts/#resources-and-statements
> > >>says: "blank nodes do not denote specific resources".  I don't
> > >>think
> > >>that is quite correct, since a blank node *does* denote a specific
> > >>resource.  It just doesn't give that resource a name that is meaningful
> > >>outside the graph.  I suggest rewording this as "blank nodes do not have
> > >>stable names that can be referenced outside of the graph".
> > >
> > >Andy explained off list that this was worded this way to avoid implying
> > >that a bnode implies a unique, identifiable individual, since a bnode is
> > >like an existential variable.  My concern was that it should be clear
> > >that when someone writes (in the same graph):
> > >
> > >  _:b1 a :Dog .
> > >  _:b1 :name "Rex" .
> > >
> > >both statements (when applied) refer to the *same* (unspecified) dog,
> > >which has (for the purposes of this graph) been called _:b1, though
> > >there may be more than one dog that satisfies these statements.  So I
> > >guess the wording here is tricky, and I'm unsure of how to make it
> > >clearer.
> > >
> > >How about "blank nodes do not indicate unique, identifiable resources"?
> > >Would that be better?  I'm okay with leaving it as is if you think not.
> > 
> > "blank nodes indicate the existence of a thing, without providing a
> > name for that thing."
> 
> +1
> 
> doesn't get involved in assumptions of uniqueness which exist at the
> graph-level (e.g. SPARQL) but not in RDF-Entailment or OWL.

The only problem is that that phrasing says that the blank node does not
have a name, when _:b1 obviously *is* a name, it just isn't a *stable*
name.  Maybe say ". . . without providing a *stable* name for that
thing"?


-- 
David Booth, Ph.D.
http://dbooth.org/

Opinions expressed herein are those of the author and do not necessarily
reflect those of his employer.
Received on Thursday, 19 July 2012 13:40:17 UTC

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