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Re: Reminder: pending discussion "membership" (pending discussion on ACTION-350)

From: Michael Kifer <kifer@cs.sunysb.edu>
Date: Fri, 07 Dec 2007 12:36:58 -0500
To: "Paul Vincent" <pvincent@tibco.com>
Cc: "Dave Reynolds" <der@hplb.hpl.hp.com>, "Public-Rif-Wg \(E-mail\)" <public-rif-wg@w3.org>
Message-ID: <10633.1197049018@cs.sunysb.edu>



> > You took my quote out of context. 
> 
> Oops. Apologies. " In the case of the Semantic Web stack, of which RIF
> is a part ..." I read as an unconditional declaration of RIF being a
> part of the semantic web, which could be misinterpreted, and is
> therefore a statement to avoid IMHO. 
> 
> > My point was there are different
> > stacks RIF might want to work with each of which already has their own
> > way of handling these things.
> 
> Fully agree. 
> 
> > Sounds like you have a use case to share! Christian has previously
> said
> > this would be very unusual in PR applications.
> 
> It may certainly be unusual for *interchangeable* PR applications, but a
> subclass mechanism may be used as a convenient way to store a local
> result in objects that are not needed outside the rule system.
> 
> Example: for electronic contract exchange, I may used a corporate
> contract XML schema, but find that I want to store intermediate rule
> processing results inside the rule engine for other rules to use. So I
> may subclass Econtract to EcontractForServices and add an attribute
> AppropriateSkillLevelApplied, computed from some other data. I use this
> in the rules but the external class / XML schema is not under my
> control.
> For interchange I would probably solve this some other way eg with a
> local XML schema of extensions, or I would force a fix to the external
> schema, etc.
> 
> Most PR engines are implemented in a 3GL / import XML (etc) into a Java
> representation, which allows them some flexibility over object model
> definitions. So subclassing an XML-derived class is not a big issue. But
> it is NOT of interest to try and standardize these mechanisms (I
> suggest) in RIF. Hence I fully concur with Christian (PRD should not
> bother with such a mechanism).
> 
> However, I can fully understand why an AI-type / knowledgebase
> application would want to include / embed schema info into its
> knowledgebase. Its just that this is not "core" to "RIF" IMHO.

We have agreed at the last F2F that BLD is **not** core and that a profile
mechanism should be developed. The core will be a subset of RIF BLD.


	--michael  


> Paul Vincent
> TIBCO | ETG/Business Rules 
>  
> 
> > -----Original Message-----
> > From: Dave Reynolds [mailto:der@hplb.hpl.hp.com]
> > Sent: 07 December 2007 09:22
> > To: Paul Vincent
> > Cc: Public-Rif-Wg (E-mail)
> > Subject: Re: Reminder: pending discussion "membership" (pending
> discussion
> > on ACTION-350)
> > 
> > Paul Vincent wrote:
> > >> Using your data modelling language of choice. In the case of the
> > >> Semantic Web stack, of which RIF is a part, the answer is RDFS/OWL.
> > >
> > > Semantics schemantics. RIF includes non sem web
> requirements/features
> > > etc, so it at best is a "shared part" of the Sem Web stack. IMHO. :)
> > 
> > You took my quote out of context. My point was there are different
> > stacks RIF might want to work with each of which already has their own
> > way of handling these things.
> > 
> > At previous F2F we've agreed that the two important stacks it needs to
> > work with are semweb and XML.
> > 
> > The sentence you quoted was saying "*if* you are working in semweb
> then
> > ...". Likewise the next one was saying "*if* you are working in XML
> > Schema then ...".
> > 
> > >> I am convinced that including these primitives moves RIF from the
> > > domain
> > >> of rule interchange into that of data model interchange. Had that
> been
> > >> explicitly part of the RIF charter I am not certain we would have
> > >> approved the formation of RIF.
> > >
> > > Funny I originally drafted a similar point in my other response, on
> the
> > > premise that Michael used the term "knowledgebase" instead of
> rulebase,
> > > and that a Knowledge Interchange Format should be considered an
> > > extension to RIF, if a KIF is desired.
> > >
> > > But, pragmatically, quite often rulebases (eg in PR) include things
> like
> > > local variable definitions, and sometimes even local subclass
> > > definitions, to simplify rule language expressions when the domain
> > > schema is "fixed" and needs "extending" in the rule system. So I
> have
> > > some sympathy for Michael's position.
> > 
> > Sounds like you have a use case to share! Christian has previously
> said
> > this would be very unusual in PR applications.
> > 
> > > 1. For the RIF use cases, we would typically want (for PR) an XML
> doc +
> > > schema to form the factbase.
> > 
> > Exactly. So how are subclass relations supposed to be connected to XML
> > Schema?
> > 
> > Dave
> > --
> > Hewlett-Packard Limited
> > Registered Office: Cain Road, Bracknell, Berks RG12 1HN
> > Registered No: 690597 England
> > 
> > 
> > > 2. The RIF charter implies (per my reading) that anything outside of
> the
> > > definition of rule should be considered a non-core extension.
> > >
> > > 3. The AI / Sem Web community are divided on the value of class
> > > membership constructs in BLD.
> > >
> > > My simple inference from this discussion that perhaps BLD should be
> > > BLCore (no "schema features") and BLDialect (BLCore + "schema
> > > features")?
> > >
> > > Paul Vincent
> > > TIBCO | ETG/Business Rules
> > >
> > >
> > >> -----Original Message-----
> > >> From: public-rif-wg-request@w3.org
> > > [mailto:public-rif-wg-request@w3.org]
> > >> On Behalf Of Dave Reynolds
> > >> Sent: 07 December 2007 08:52
> > >> To: Michael Kifer
> > >> Cc: axel@polleres.net; Public-Rif-Wg (E-mail)
> > >> Subject: Re: Reminder: pending discussion "membership" (pending
> > > discussion
> > >> on ACTION-350)
> > >>
> > >>
> > >> Michael Kifer wrote:
> > >>> CSMA had an action to bug me about the ## feature :-)
> > >>> I thought that others might also be interested, so I am including
> my
> > >>> arguments below.
> > >>>
> > >>> First, one needs to be able to specify that one class is a
> subclass
> > > of
> > >>> another class **as part of the KB**.
> > >> I disagree, at least if by KB you mean RIF rules rather than RIF
> rules
> > > +
> > >> externally specified ontology or data model.
> > >>
> > >> Expressing data models or ontological models and any subClass
> > > relations
> > >> associated with them is not a RIF requirement.
> > >>
> > >>> For instance,
> > >>>
> > >>> student##person.
> > >>> father(person)##person.
> > >>>
> > >>> In KB apps this is used for reasoning, not just as part of a data
> > >>> model. How would one specify this info otherwise?
> > >> Using your data modelling language of choice. In the case of the
> > >> Semantic Web stack, of which RIF is a part, the answer is RDFS/OWL.
> > >>
> > >> In the case of XML Schema models then complex types can be related
> by
> > >> both extension and restriction in ways that don't neatly map to
> > > subClass.
> > >>> Here is a more sophisticated example: parametrised lists.
> > >>>
> > >>> list(?Subclass) ## list(?Super) :- ?Subclass ## ?Super.
> > >>>
> > >>> (List of FOOs is a subclass of lists of BARs if FOO is a subclass
> of
> > >>> BAR. We could have list(father(person)), for example.)
> > >>>
> > >>> RDF's subclassOf does not cut it because
> > >>>
> > >>> 1. It imposes additional axioms, which are not commonly accepted.
> > >>> 2. It is also not even defined for classes specified using
> function
> > >> terms
> > >>>    (like list(?Foo)).
> > >>>
> > >>> Both arguments are also applicable to the RDF membership
> > > relationship.
> > >>> I am convinced that throwing out these primitives serves no
> purpose
> > > and
> > >>> will just gratuitously cripple the BLD.
> > >> I am convinced that including these primitives moves RIF from the
> > > domain
> > >> of rule interchange into that of data model interchange. Had that
> been
> > >> explicitly part of the RIF charter I am not certain we would have
> > >> approved the formation of RIF.
> > >>
> > >> Dave
> > >> --
> > >> Hewlett-Packard Limited
> > >> Registered Office: Cain Road, Bracknell, Berks RG12 1HN
> > >> Registered No: 690597 England
> > >
> 
> 
> 
> 
Received on Friday, 7 December 2007 17:37:10 GMT

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