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Re: Evidence of user attitudes toward BNodes (was Re: Proposal and Test cases (Re: skolems: visible differences?))

From: Jeremy Carroll <jjc@hpl.hp.com>
Date: Wed, 23 Jan 2008 15:11:22 +0000
Message-ID: <4797591A.1080501@hpl.hp.com>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: "Web Ontology Language ((OWL)) Working Group WG" <public-owl-wg@w3.org>

I read that differently

Fred's concern appears to be about unique names assumption
I think the naive view is that two things are distinct if they
look distinct.  Two IRIs that are spelled differently are
different.  Two blank nodes with different node identity
are different.  (Blank node identifiers are proxies for node
identity; two blank nodes with different identifiers are

this is pertinent because blank nodes basically are blank and don't have 
names (particularly in RDF/XML).

My reading is that e-mail is phrased as concession to users naive 
expectation of unique names - the OWL 1.1 DL user with such an 
expectation will come unstuck many times over in a whole variety of places.

The naive SPARQL user may have greater success.


Bijan Parsia wrote:
> I want to re-emphasize: Handling bnodes as singular terms (i.e., names) 
> is, for me, primarily driven by user considerations. The fact that 
> BNodes as variables make reasoning much harder (even in RDFS) is a 
> strong consideration, but given that BNodes as variables are not what 
> users want or expect *or* what systems (including RDF systems) give 
> them, is by far the strongest, and I would say overwhelming, reason.
> In the last telecon, I said:
>     Bijan Parsia: In the sparql working group, people like, Oracles Fred 
> Zemke, clearly believed that bnodes were singular terms.
> I tracked down the email that I recall backed this up:
>     http://lists.w3.org/Archives/Public/public-rdf-dawg/2006JulSep/0008.html 
> To be precise, I think Fred clearly believed that they *should be* 
> singular terms.
> """The user is relying on distinct
> blank nodes to represent distinct line items.
> Of course, from the point of view of "RDF Semantics"
> that would be a redundant graph, for example, one that
> asserts "There exists a line item whose part is XYZ,
> quantity is 1 and price is 10.99" and asserts again
> "There exists a line item whose part is XYZ, quantity is 1 and
> price is 10.99".  Thus one could say that this is a misuse
> of RDF.  This may be technically true, but I wonder if insisting
> on this point will really serve the users.  If you read the RDF
> Primer, the application design above makes sense. You have a line
> item; you don't want to bother creating an IRI for each line
> item; so you make a blank node for each line item."""
> Cheers,
> Bijan.
Received on Wednesday, 23 January 2008 15:20:25 UTC

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