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Re: RIF Core, and how much is PRD allowed to diverge from BLD [Was: Re: [PRD] Issues to resolve before publication]

From: Mark Proctor <mproctor@redhat.com>
Date: Tue, 01 Jul 2008 13:44:34 +0100
Message-ID: <486A26B2.8090606@redhat.com>
To: Dave Reynolds <der@hplb.hpl.hp.com>
CC: "Boley, Harold" <Harold.Boley@nrc-cnrc.gc.ca>, Gary Hallmark <gary.hallmark@oracle.com>, Christian de Sainte Marie <csma@ilog.fr>, RIF WG <public-rif-wg@w3.org>

Dave Reynolds wrote:
> Boley, Harold wrote:
>> Production Rule languages such as the widely used CLIPS
>> (http://en.wikipedia.org/wiki/CLIPS) employ predicates
>> like car_problem with named arguments.
> I wasn't talking about named arguments in general but the specific 
> case of "named argument uniterms with the semantics as defined in BLD" 
> which is what I took the term "NAU" to stand for.
>> CLIPS (Wikipedia rule1 is a "pure production rule"):
>> (deffacts trouble_shooting
>>     (car_problem (name ignition_key) (status on))
>>     (car_problem (name engine) (status wont_start))
>>     (car_problem (name headlights) (status work))
>>  )
> In CLIPS those are "unordered facts" (or deftemplate facts) and I 
> believe you can partially match against them. For example you could 
> also have a rule:
> (defrule rule1
>     (car_problem (status wont_start))
>      =>
>     (assert (car_problem (name suspectedStarter))
>  )
> and it would still match those facts even though some arguments are 
> missing.
yes this is correct. Named arguments on a pattern is a subset of the 
available fields on the fact.
> Thus I believe the CLIPS representation corresponds to more closely 
> frames in RIF not to NAUs. I would certainly include Frames in core.
I still dislike that Frames insist on an OID, would be happier if that 
could be dropped. Whole point with a pattern is that it's not pointing 
to a specific instance. I understand that this can be hidden as an 
implementation detail, I still think it's a cludge.
> My knowledge of CLIPS only comes from checking the online manuals not 
> from deep experience so I would be prepared to corrected on this.
If you have any PR Qs you, or anyone else, can ping me on irc #drools @ 
irc.codehaus.org (web gateway provided)
> Dave
>> (defrule rule1
>>     (car_problem (name ignition_key) (status on))
>>     (car_problem (name engine) (status wont_start))
>>      =>
>>     (assert (car_problem (name starter) (status faulty))
>>  )
>> RIF-BLD (simplified, with rule1 as a Horn-like rule):
>> (* trouble_shooting *)
>> car_problem(name->ignition_key  status->on)
>> car_problem(name->engine        status->wont_start)
>> car_problem(name->headlights    status->work)
>> (* rule1 *)
>> car_problem(name->starter       status->faulty) :-
>>   And(
>>       car_problem(name->ignition_key  status->on)
>>       car_problem(name->engine        status->wont_start) )
>> -- Harold
>> -----Original Message-----
>> From: public-rif-wg-request@w3.org [mailto:public-rif-wg-request@w3.org]
>> On Behalf Of Gary Hallmark
>> Sent: June 30, 2008 6:35 PM
>> To: Dave Reynolds
>> Cc: Christian de Sainte Marie; RIF WG
>> Subject: Re: RIF Core, and how much is PRD allowed to diverge from BLD
>> [Was: Re: [PRD] Issues to resolve before publication]
>> I'm sure the word "core" is overloaded and means many things to many 
>> people.
>> Right now, I'm concerned with an operational meaning, which is literally
>> the intersection of BLD and PRD.  The larger this intersection, the 
>> better.  I don't care so much for NAU per se, I just use it as an 
>> example.  Because it is in BLD, the default should be that it is in 
>> PRD as well, unless there is some evidence that it is more difficult 
>> for PRD
>> than for BLD.  There is no such evidence -- in fact, it is common in PRD
>> (Jess and CLIPS have it)
>> Dave Reynolds wrote:
>>> Gary Hallmark wrote:
>>>> To maximize rule interchange between production rule engines and 
>>>> logic rule engines, clearly Core should be "as big as possible".  
>>>> We can, should, and must decide that now.  I don't even know why I 
>>>> have to keep arguing this point.  The bias to keep BLD and PRD 
>>>> aligned with a large common core should be so high that the burden 
>>>> of proof is on you to show why NAU  should not be in Core.  You 
>>>> have provided no such proof.
>>> I haven't followed all the ins and outs of all this discussion but 
>>> even without PRD I'm not immediately convinced NAU should be in core.
>>> They seem relatively uncommon in rule languages. They got in, in the 
>>> end, on the grounds that they can be handled at the translation 
>>> stage for languages that don't support them. However, the notion of 
>>> a "Core"
>>> suggests some criteria of simplicity and minimality and there needs to
>>> be a higher burden of proof that these extra syntactic features have 
>>> value in the Core.
>>> Dave

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Received on Tuesday, 1 July 2008 12:48:20 UTC

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