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Re: Issue-12 and the next UCR draft

From: Bijan Parsia <bparsia@cs.man.ac.uk>
Date: Wed, 13 Sep 2006 17:20:23 +0100
Message-Id: <0F9AF139-F6B8-4345-A696-5F506366888C@cs.man.ac.uk>
Cc: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>
To: axel@polleres.net

On Sep 13, 2006, at 4:43 PM, Axel Polleres wrote:

> Sandro Hawke wrote:
>>> There are deep issues with BNodes that have hurt us in SPARQL,  
>>> and I  think most extant SemWeb rule languages largely punt on  
>>> them. It  would be good to deal with them properly. (e.g., are  
>>> BNodes scoped to  the document? Even when they appear in rules?)
>> Is it clear enough how RDF with BNodes maps to FOL?  I'm hoping  
>> RIF can
>> avoid paying attention to the details of BNodes by thinking of RDF as
>> simply a fragment of FOL and BNodes as a constrained syntax for
>> existential variables.
>
> The following article clarifies this matter:
>
> Jos de Bruijn, Enrico Franconi, and Sergio Tessaris. Logical  
> reconstruction of normative RDF. In OWL: Experiences and Directions  
> Workshop (OWLED-2005), Galway, Ireland, November 2005.
>
> http://www.debruijn.net/publications-type/bruijn05:_logic_rdf2.html

Good pointer.

Sandro, the problem is that most extant rule languages do *not* treat  
BNodes as existentials, but skolemize them in a variety of ways.  
There are subtle and tricky issues esp. when talking with people with  
different views of how they work. Then, once you have agreement  
there, how they integrate with logic programming type rules is,  
again, very tricky. It's a research topic on its own and many of the  
extant rule languages have not attended to them (which is fine,  
except for poor standards bodies that have to harmonize with existing  
specifications).

Grumpy dragons this way lie.

Cheers,
Bijan.
Received on Wednesday, 13 September 2006 16:20:26 GMT

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