Re: RIF Core shortened

I do not know what an "externally defined data model" is.  I like the 
SWC model, where one can import an RDF graph or OWL ontology.  But the 
semantics is defined by mapping those imported things to the RIF data 
model, i.e. herbrand terms and frames.  I think a similar approach works 
for schema-valid XML.  But that may mean, depending on how one 
interprets what an external data model is, that it is precisely the 
facts of the form o#C where C is imported from an XML document (is this 
an external data model?) that is needed.

Christian de Sainte Marie wrote:
>
> (Executive summary for those who do not read long emails:
>
> <<[...] my analysis (at this point) is that we may allow the assertion 
> of:
> - facts of the form o#C if and only C is not part of an externally 
> defined data model, except in the only case of object creation;
> - facts of the form sub##SUP if and only if sub and SUP are not both 
> part of the same externally defined data model, with no exception.>>
>
> See explanations and details below.)
>
> Gary Hallmark wrote:
>
>> Core (and thus BLD and PRD) needs to be able to represent facts and 
>> rules.  Here are some examples of facts:
>
> No contest about that: the Assert action in PRD really only asserts 
> facts (ground atomics). Even membership and subclass facts, why not: 
> if Core and BLD need it, in the case where the data model is not 
> externally defined (that would not be the most prominent use case for 
> PRD, and thus maybe a bit more difficult to implement; but not 
> infeasible; at least, worth considering).
>
> So, as I understand it, the question is, really, whether we want to 
> allow the assertion of membership facts when the class belongs to an 
> externally defined data model, and why; and, even more, whether we 
> want to allow the assertion of subclass facts when one or both classes 
> belong to an externally defined data model, and why.
>
> As far as I can see, the only use case for asserting a membership fact 
> when the class is part of an externally defined data model is object 
> creation (where the fact that the new object is a member of its class 
> must be asserted). Are there other use cases?
>
> If not, first, Core and BLD do not need it; and, second, wouldn't 
> embedding that specific assertion in the "New" action do the trick 
> without requiring that the assertion of membership be allow in general 
> (as proposed in [2])?
>
> Regarding the assertion of subclass facts, I can see no case where it 
> makes sense if both classes (the subclass and the superclass) are 
> defined as part of the same externally defined data model (since, 
> indeed, that fact is externally defined).
>
> If one of the classes involved in the subclass fact is not part of an 
> externally defined, then no problem: asserting such subclass facts 
> amount to link an internally defined data model (that is, a data model 
> defined by the rule set itslef) to an externally defined one.
>
> And if both classes are part of different externally defined data 
> models, then, why not: that would amount to define internally a new 
> data model that links the externally defined ones. I do not know 
> whether there are use cases, but I do not see an issue in principle.
>
> So, my analysis (at this point) is that we may allow the assertion of:
> - facts of the form o#C if and only C is not part of an externally 
> defined data model, except in the only case of object creation;
> - facts of the form sub##SUP if and only if sub and SUP are not both 
> part of the same externally defined data model, with no exception.
>
> We "may", but we do not necessarily "want" or "need" to: the question, 
> here, is whether or not we want or need to make RIF a format for 
> interchanging data models as well as rules. But that is a different 
> question (issue-48 [1])
>
> [1] http://www.w3.org/2005/rules/wg/track/issues/48
> [2] http://www.w3.org/2005/rules/wiki/Alt_AbstrAction
>
> Cheers,
>
> Christian
>
>

Received on Tuesday, 18 November 2008 16:33:04 UTC