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Re: Urgent: Issue with RIF-Core EBNF Grammar?

From: Axel Polleres <axel.polleres@deri.org>
Date: Wed, 12 May 2010 12:23:39 +0100
Cc: "Dave Reynolds" <dave.e.reynolds@googlemail.com>, "Christian De Sainte Marie" <csma@fr.ibm.com>, "RIF" <public-rif-wg@w3.org>
Message-Id: <CCC281E3-B7D6-45B4-B98B-25EEDA23CAF5@deri.org>
To: Jos de Bruijn <jos.debruijn@gmail.com>

On 12 May 2010, at 11:19, Jos de Bruijn wrote:

> 
> 
> On 05/12/2010 12:09 PM, Dave Reynolds wrote:
> > On 12/05/2010 09:36, Jos de Bruijn wrote:
> >> Axel, Christian, all,
> >>
> >> I raised my concerns about the RIF-Core spec in a separate email.
> >>
> >> Concerning facts about class membership: they are both in BLD and PRD
> >> (see [1]).
> >> Concerning class membership atoms in rule conclusions: I do remember
> >> that we explicitly forbade them in Core.
> >
> > That's my recollection too.
> >
> > Our official record of the decision [1] was to allow membership "in Core
> > facts and conditions".
> >

So, my vague memories were at least right until this point, phew :-)

> > We did at one point have an EBNF that reflected that resolution.
> >
> > My memory [2] was that Gary on behalf of the PRD group later pointed
> > that asserting membership facts was just as problematic as concluding
> > them via non ground rules. The problem being that in object-based PR
> > implementations membership is hardwired in the external data model.
> 
> Then I find it strange that PRD allows asserting class membership facts.

Indeed, that makes it double weird... if the change to disallow them in Core 
came from PRD, then why is it now ALLOWED in PRD to assert membership facts 
but forbidden in Core? ... /me seriously confused.


> > So
> > we decided to forbid any assertion of membership facts. I.e. the EBNF
> > accurately reflects our intention[3].
> >
> > The phrasing in section 2.3 is clarified by "they [equality terms and
> > class membership terms] are only allowed in rule premises". I agree that
> > the term rule "premise" is not defined in the document so it could be
> > clearer but I don't see how one could reasonably interpret a ground fact
> > as a "premise".
> 
> I agree that a ground fact could not be interpreted as a premise.
> However, it is unclear in the phrasing whether the last part of the
> sentence applies to all formulas or only to rules (whatever they may be).

true. I understand that we probably have to stick with what we have, but 
at least a small clarification/rephrasing of that point in 2.3 would be 
good to add.

Axel



> 
> Best, Jos
> 
> > So it seems to me the normative text and informative
> > EBNF are in agreement.
> >
> > Dave
> >
> > [1] http://www.w3.org/2005/rules/wg/track/issues/48
> > [2] Which I've not been able to validate from the record trail.
> > [3] That intention may be strange and hard to understand but that's the
> > nature of working group compromises :)
> 
> --
> Jos de Bruijn
>   Web:          http://www.debruijn.net/
>   LinkedIn:     http://at.linkedin.com/in/josdebruijn
> 
Received on Wednesday, 12 May 2010 11:24:13 GMT

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