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

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Thu, 19 Jul 2012 15:52:25 +0200
Message-ID: <50081119.6020203@emse.fr>
To: public-rdf-comments@w3.org
I'm afraid I'll repeat myself but a blank node does *not* have a name, 
it is blank. _:b1 is an artifact of the serialisation syntax you used. 
It does not exist in the RDF graph.
Basically, you just wrote this:

[] a :Dog; :name "Rex" .

or that:

    <rdf:type rdf:resource="Dog"/>

where is the name of the bnode?


Le 19/07/2012 15:39, David Booth a écrit :
> 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"?

Antoine Zimmermann
ISCOD / LSTI - Institut Henri Fayol
École Nationale Supérieure des Mines de Saint-Étienne
158 cours Fauriel
42023 Saint-Étienne Cedex 2
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
Received on Thursday, 19 July 2012 13:52:49 UTC

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