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Re: Blank nodes semantics - existential variables?

From: Antoine Zimmermann <antoine.zimmermann@emse.fr>
Date: Tue, 23 Jun 2020 13:11:32 +0200
To: semantic-web@w3.org
Message-ID: <a412fb24-db4e-19c1-d758-61fdf07bc2f7@emse.fr>

Le 21/06/2020 à 15:35, angin scribe a écrit :
> Hi everyone,
> Is the standard semantics of blank nodes in RDF still the same as 
> existentially quantified variables?


> Let "_:b1" and "_:b2" be blank nodes, In the current standard semantics 
> of RDF, is it still true that the graph below does not necessarily mean 
> that Bob has two different things?
> Bob has _:b1
> Bob has _:b2

Indeed. This graph would be equivalent to saying:

"Bob has something. Bob has something."

We can't conclude that Bob has 2 things.

> I.e., two syntactically different blank nodes do not necessarily mean 
> that they are two different entities.
> I know that there has been a lot of discussion on blank nodes in the 
> past, cf. [1, 2, 3]. I just want to make sure that there are no recent 
> changes on the semantics of blank nodes that I missed. Please let me 
> know if I miss some recent updates in this area. Many thanks!

In standardising Web technologies, the W3C is extremely cautious about 
backward compatibility. If something was defined in some way in a 
version of a W3C standard, it is likely to work the same in later 
versions. Sometimes, features get deprecated, but they still work the 
same, if used. Other times, features get added, but they do not change 
the way prior features work. Obviously, there are exceptions, even in 
RDF. For instance, the way literals and datatypes work in RDF 1.1 is 
different from RDF 1.0, but the practical consequences are almost 


> Cheers,
> A
> [1] M. Arenas, M. Consens. A. Mallea. Revisiting Blank Nodes in RDF to 
> Avoid the Semantic Mismatch with SPARQL. 
> https://www.w3.org/2009/12/rdf-ws/papers/ws23
> [2] A. Hogan, M. Arenas, A. Mallea, A. Polleres. Everything You Always 
> Wanted to Know About Blank Nodes. Journal of Web Semantics. 2014.
> [3] A. Mallea, M. Arenas, A. Hogan, A. Polleres. On Blank Nodes. ISWC 2011.

Antoine Zimmermann
Institut Henri Fayol
École des Mines de Saint-Étienne
158 cours Fauriel
CS 62362
42023 Saint-Étienne Cedex 2
Tél:+33(0)4 77 42 66 03
Fax:+33(0)4 77 42 66 66
Member of team Connected Intelligence, Laboratoire Hubert Curien
Received on Tuesday, 23 June 2020 11:11:47 UTC

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