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In defence of Bnodes - Re: AW: {Disarmed} Re: blank nodes (once again)

From: Henry Story <henry.story@bblfish.net>
Date: Thu, 24 Mar 2011 23:40:37 +0100
Cc: Sandro Hawke <sandro@w3.org>, Michael Schneider <schneid@fzi.de>, Graham Klyne <GK-lists@ninebynine.org>, Dieter Fensel <dieter.fensel@sti2.at>, Enrico Franconi <franconi@inf.unibz.it>, Hugh Glaser <hg@ecs.soton.ac.uk>, Mark Wallace <mwallace@modusoperandi.com>, Alan Ruttenberg <alanruttenberg@gmail.com>, Reto Bachmann-Gmuer <reto.bachmann@trialox.org>, Ivan Shmakov <oneingray@gmail.com>, Ivan Shmakov <ivan@main.uusia.org>, "<semantic-web@w3.org>" <semantic-web@w3.org>
Message-Id: <EF943C2F-A0E1-4E6F-822F-E4EDE7DAD14A@bblfish.net>
To: Pat Hayes <phayes@ihmc.us>
Some thoughts on the advantages of bnodes to linked data:

- when you give something a name, you are clearly asking/allowing people to use your reference again, link to it, and so on. A bnode gives you the option of not taking that responsibility. 
- there is distinction in philosophy of descriptions and names. You can speak of something both ways. It seems that bnodes must function as things referred to by description. So the modal properties of such things won't be the same. 
- continuing on that thought, a graph with a bnode tells you which part is being described and which parts are being referred to.  So this makes me thing of Bertrand Russel's theory of definite descriptions, "the king of france is bald"
  [] a KingOfFrance, Bald.

 with some restrictions on the KingOfFrance set being a singleton I suppose.

I am not sure where this leads, but it just seems that there are pragmatic and perhaps modal reasons for bnodes


On 24 Mar 2011, at 19:54, Pat Hayes wrote:

> Another quick thought...
> On Mar 24, 2011, at 12:14 PM, Pat Hayes wrote:
>> ....
>>>> The one possible exception I can see is the use of bnodes to encode OWL syntax, using the RDF list construction. Clearly, one does not want to have OWL/RDF entailments ruined because a list has been given a name. This might require some special conventions; but in practice, again, this use of RDF has never been seriously intended to be used by RDF inference engines. Rather, this 'encoding' of OWL uses RDF as a serialization mechanism to move OWL around the Web via RDF portals. If we were to make this explicit, we could isolate this from RDF entailment regimes altogether. Which now that I think about it, might be a very good idea. 
>>> Is there something in the OWL specs that says OWL doesn't work (or that
>>> we're no longer in DL) if the nodes composing the lists are not blank?
>> Not actually a statement, but the entailments would not work in the same way. (To see why, consider some OWL/RDF and skolemize it two different ways. These two are identical OWL but do not entail one another in RDF.) Yes, this would be a problem. The OWL/RDF spec would have to be re-written. ...
> Maybe not. Consider a version of RDF in which bnodes are allowed but ONLY in triples encoding RDF collections. They have no semantics, but are treated simply a a syntactic device to string lists together: they are just part (along with the RDF collections vocabulary) of a kind of RDF-specific syntax trick to encode S-expressions in RDF triple syntax. This leaves the OWL specs entirely alone, and still removes blank nodes from the 'real' RDF data, where they are skolemized. 
> Inelegant, but it solves all the practical problems.
> Pat

Social Web Architect
Received on Thursday, 24 March 2011 22:41:15 UTC

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