RE: ISSUE-43: Subclass relationship ## in RIF-BLD

Thanks Michael,

> Objections have been raised to the inclusion of the subclass relationship,
> a##b, in RIF-BLD on the grounds that it duplicates rdfs:subclassOf.

I think it would make sense to generalise the objection to:
<<
RIF including subclass (and other similar metamodel-type relationships?) duplicates the data model specifications used to provide data for RIF rules. >>

I have to say I am neutral on the topic - with maybe a slight preference for keeping it out of RIF BLD on the basis that 
- BLD is (AFAIK) meant to be a "common dialect subset", 
- subclass relationships are simply a special type of relationship test (eg why not consider PartOf relationships?) (or maybe relationship assertion),
- in Prod Rules we "generally generalize" to "memberOf" ie X is a memberOf parts of Y or subclasses of Y (etc). Due to most PR languages using Java as their base object model, and with multiple inheritance being passé in that world, OO / frame relationship tests tend to be rare* (to say the least), and assertions - well...  

But I understand this issue is of much more importance to the KR folk, which is why I am officially neutral (for now!).

Paul Vincent
TIBCO | ETG/Business Rules 

PS: * You could argue that logically, PR are often testing for "subclass" - its just the the object model implementation / used for writing the rules is not defined in a pure (multiple inheritance) OO fashion, so the data model is "flattened" compared to other OO models ...
 

> -----Original Message-----
> From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
> On Behalf Of Rule Interchange Format (RIF) Working Group Issue Tracker
> Sent: 16 October 2007 17:10
> To: public-rif-wg@w3.org
> Subject: ISSUE-43: Subclass relationship ## in RIF-BLD
> 
> 
> 
> ISSUE-43: Subclass relationship ## in RIF-BLD
> 
> http://www.w3.org/2005/rules/wg/track/issues/43
> 
> Raised by: Michael Kifer
> On product: Architecture
> 
> Objections have been raised to the inclusion of the subclass relationship,
> a##b, in RIF-BLD on the grounds that it duplicates rdfs:subclassOf.
> 
> Defenders of this relationship state that:
> 
> 1. Subclass relationship is a common and very basic concept of any
>    object-oriented/frame representation, and frame representation
> requirement
>    is in the Charter.
> 
> 2. The rdfs:subclassOf relationship is not a standard subclassOf
> relationship.
>    Using it instead of ## introduces additional axioms into the semantics,
>    which are not supported by standard object-oriented languages.
> 
> 3. Not including ## in the language means that systems like FLORA-2,
>    Ontobroker, FLORID, etc. must invent a new dialect to exchange their
>    Horn subsets just because ## is not included.
> 
> 4. Excluding this construct precludes us from stating simple things like
>    bar##foo (i.e., bar is a subclass of foo) without carrying the baggage
>    of the additional axioms of rdfs:subclassOf.
> 
> 5. ## does not preclude the use of rdfs:subclassOf for languages that want
>    to use RDFS' notion of subclass.
> 
> 
>

Received on Tuesday, 16 October 2007 17:03:26 UTC