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Re: ACTION-420 Review of SW-compatibility

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Tue, 11 Mar 2008 09:51:05 +0100
Message-ID: <47D647F9.9000907@inf.unibz.it>
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: axel@polleres.net, RIF <public-rif-wg@w3.org>

>> Well, the RDF model theory gives a precise definition.
>> In short, like any other symbol, a blank node is mapped to an element 
>> in the domain.  Then, satisfaction of triples is determined by the 
>> extension function IEXT: IP -> 2^{IR x IR}.
> Interesting...this suggests that blank nodes are not treated as 
> variables (but as constants)?

No.  Both blank nodes and names are mapped to objects in the domain. 
The former are mapped using a blank node mapping; the second are mapped 
using an interpretation.

> (I ask because this is in heavy debate in the OWL WG...if RIF is going 
> to be playing with RDF (e.g., generalizing it) it's probably important, 
> or at least helpful, to coordinate.

Indeed.  Although, RIF does not propose to generalize RDF as such. If we 
merely define interoperability with respect to a superset of RDF.

>>>> The reason we consider extended RDF graphs is to accommodate 
>>>> possible extensions of RDF that are less restrictive in their syntax.
>>> So, can we define both a general framework plus one compatibility 
>>> notion actually compatible with current RDF? That would be fine with me.
>> The current notion is completely 100% compatible with standard RDF, 
>> since every standard RDF graph is a generalized RDF graphs, and the 
>> semantics is exactly the same.
>> I just see three options:
>> 1 define compatibility only with respect to standard RDF
>> 2-define compatibility with respect to generalized RDF
>> 3- define compatibility with respect to "semi-generalized" RDF, in 
>> which you would not have literals and blank nodes in property positions
> [snip]
> 3 is akin to what sparql allows, yes? I guess that provides *some* reason.

I guess so.

Best, Jos

> Cheers,
> Bijan.


Jos de Bruijn,        http://www.debruijn.net/
One man that has a mind and knows it can
always beat ten men who haven't and don't.
   -- George Bernard Shaw

Received on Tuesday, 11 March 2008 08:51:26 UTC

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