Re: To embed or combine

Michael Kifer wrote:
>>> <chair>
>>> The status of the discussion regarding Jos' RDF compatibility section
>>> appears to be mired in whether the normative semantics of RDF in RIF
>>> should be specified in the model theory through a "combination" of RIF
>>> and RDF semantics, or through an "embedding" of RDF semantics in RIF (as
>>> rules).  The two approaches have been shown by Jos to be equivalent.
>> The two approaches are only equivalent with respect to entailment. If
>> you want to extend either language (RDF for RIF), then they will differ.
>>
>>> At the moment I have not seen any technical arguments supporting one
>>> approach or the other. 
>> There are two main technical arguments for the model-theoretic approach:
>>
>> i) It directly extends the RDF (as well as the RIF) model theoretic
>> semantics, and is thus *by definition* faithful to the semantics.
>>
>> ii) The approach is extensible, in the sense that it can be immediately
>> used for any semantic extension of RIF (or RDF, for that matter), such
>> as counting. The embedding of RDF in RIF would have to be reevaluated
>> for most kinds of extensions of RIF, in order to make sure the
>> entailments are the ones you might expect.
> 
> And your semantics will not need to be reevaluted for most kinds of
> extensions of RIF & RDF? 

You have a point there. Extension towards rules with nonmonotonic
negation is not straightforward.


Best, Jos

> 
> 
> 	--michael  
> 
> 
>> Best, Jos
>>
>>> Michael prefers the "embedding" on the basis that:
>>>
>>> (1) the "combination" is more complicated than the "embedding" and thus
>>> more difficult to understand.
>>>
>>> (2) it is not our job viz. our charter to specify a model theoretic
>>> approach to the RDF/RIF combination
>>>
>>> Jos seems to prefer the "combination" and argues re: (1) that:
>>>
>>> (3) it is no more difficult to understand the "combination" than the RIF
>>> model theory.
>>>
>>> As chair, my own read of the charter does not provide any particular
>>> help on (2), I'm not quite sure what Michael is referring to there.  It
>>> is certainly our job to specify how RIF and RDF should be used together,
>>> and as chair I interpret this as meaning we should have a normative
>>> standard for that.
>>>
>>> Thus, as suggested by Michael, it seems to me we are at a difference in
>>> preference only, and I see no alternative other than to call a vote.  It
>>> seems to me the vote is about which approaches to make *normative*:
>>>
>>> 1) The model-theoretic "combination" of RIF and RDF is normative
>>> 2) The "embedding" of RDF semantics as RIF rules is normative
>>> 3) Both the "combination" and "embedding" are normative (What would that
>>> mean?)
>>> </chair>
>>>
>>> -Chris
> 

-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
----------------------------------------------
The third-rate mind is only happy when it is
thinking with the majority. The second-rate
mind is only happy when it is thinking with
the minority. The first-rate mind is only
happy when it is thinking.
  - AA Milne