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Re: RIF Core shortened

From: Gary Hallmark <gary.hallmark@oracle.com>
Date: Fri, 14 Nov 2008 13:06:51 -0800
Message-ID: <491DE86B.3080509@oracle.com>
To: kifer@cs.sunysb.edu
CC: Dave Reynolds <der@hplb.hpl.hp.com>, "Boley, Harold" <Harold.Boley@nrc-cnrc.gc.ca>, Adrian Paschke <Adrian.Paschke@gmx.de>, Axel Polleres <axel.polleres@deri.org>, RIF WG <public-rif-wg@w3.org>

I've been schizophrenic on this issue.

I don't know how to map (schema valid) xml documents to frames without # 
and ## in rule heads (although I prefer those rules to have no bodies, I 
think that is harder to nail down). 

So I propose that core allow # and ## everywhere that BLD allows them.
Equality is allowed in the body only (for core).

Because most PR engines don't allow # and ## to be asserted except when 
the object is being created, the RIF translator may need to map # and ## 
to a union of some external predicate and a logical predicate.  I feel 
that PR translators have to bear some small reasonable burden in order 
to get non-trivial overlap with BLD, and this looks to be part of that 
burden.  I'm willing to bear it, but other folks may not.

Michael Kifer wrote:
> On Fri, 14 Nov 2008 12:24:42 +0000
> Dave Reynolds <der@hplb.hpl.hp.com> wrote:
>
>   
>> Hi Michael,
>>
>> This looks fine.
>>
>> I've done a set of very minor edits:
>>    - standardized the "safely conformant" nomenclature across the document
>>    - fixed a couple of minor formatting problems
>>    - deleted a reference to external frames
>>    - rephrased the links to BLD examples to give the numbers of the 
>> referenced example to make it possible to understand the link when 
>> reading the printed version.
>>
>> Looking at the issues you have noted:
>>
>> ** ISSUE: Did we really decide that ## cannot occur at all or that it 
>> can occur only in the rule bodies?
>>
>> The former. To be more precise we discussed this in a Core telecon and 
>> had two proposals from that:
>>
>> PROPOSED: RIF Core will not include subclass (##)
>> PROPOSED: RIF Core will include member (#) but syntactically restricted 
>> its use in rule bodies. Note that in RIF-RDF the equivalent property 
>> rdf:type would still be permitted in rule heads.
>>
>> However in the whole-WG telecons we passed the second of those but I 
>> don't think we ever formally voted on the first so technically I guess 
>> it is still open.
>>     
>
> I may have slept thought this, but I vaguely recall that there were objections
> even to removing it from the heads. I think Gary or somebody else pointed out
> that we have no way of specifying a simple subclass hierarchy without being
> able to use :: in the facts.
>
>   
>> ** ISSUE: What was decided about external functions?
>>
>> In the same RIF Core telecon we had:
>>
>> PROPOSED: Core should keep unrestricted equality and external function 
>> and predicate calls in rule bodies and keep external functions calls in 
>> rule heads.
>>
>> I haven't managed to find the formal WG adoption of that.
>>     
>
> Then the current syntax needs fixing, as it does not allow that.
>
>   
>> ** ISSUE: Need to give EBNF for RIF-Core
>>
>> Isn't that section (2.6) an EBNF for Core? Is there some specific error 
>> in that EBNF?
>>     
>
> I don't see how this EBNF enables the use of external functions.
>
> michael
>
>   
>> Michael Kifer wrote:
>>     
>>> I had couple of spare hours and decided to finish my action item ahead of
>>> time to surprise everybody.
>>>  As agreed in today's telecon, I have shortened the core significantly.
>>> So, it is now unabashedly dependent on RIF-BLD, but it is now much easier to
>>> see what is going on.
>>>
>>> The old text and its history has been moved to
>>> http://www.w3.org/2005/rules/wiki/Core-alternative
>>>
>>> I did not touch the overview. In the EBNF sections I only made references to
>>> the examples (without repeating them). The EBNF section requires drastic
>>> cuts and the actual EBNF needs to better match the core. (I forgot
>>> whether we decided to keep external functions. If not then ok.)
>>> In particular, in RIF-Core there is no need to repeat the syntax and most of
>>> the explanations. In fact, the material in this section is even
>>> longer than in BLD itself -- a stale pasted copy from an older BLD document.
>>>
>>> The conformance section also needs shortening. For instance, it is not clear to
>>> me why we should keep much of Section 5.2. Maybe we could again refer to BLD?
>>>
>>> Section 6 (PRD) hasn't been touched. It requires much attention from Gary and/or
>>> Adrian.
>>>
>>> michael
>>>       
>>
>>     
Received on Friday, 14 November 2008 21:07:58 GMT

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