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Re: [PRD] Rule instances, refraction and Modify [Was: Re: Fwd: Clips behavior]

From: Mark Proctor <mproctor@redhat.com>
Date: Tue, 03 Aug 2010 10:49:53 +0100
Message-ID: <4C57E641.70607@redhat.com>
To: Gary Hallmark <gary.hallmark@oracle.com>
CC: Christian De Sainte Marie <csma@fr.ibm.com>, Neal Wyse <neal.wyse@oracle.com>, RIF WG <public-rif-wg@w3.org>
  On 19/01/2010 16:45, Gary Hallmark wrote:
> CLIPS I think does not have "slot specific" modify but Jess, OBR, 
> Drools (I think), ILOG (I think) all have it.
Clips deftemplates does not, for Clips COOL it is the only way that 
those objects can work. Jess allows slot-specific to be configured per 
field.

Drools, JRules and OPSJ do not have slot specific (please correct me if 
I'm wrong).
> I am not in favor of treating modify as 
> retract-all-slots/reassert-all-slots because in our experience this 
> semantics makes too many common business rules loop and is very hard 
> to use.
I agree. Refraction addresses this to some degree, but it's a bit of a 
sledge hammer; "slot-specific" is more fine grained and elegant. However 
the two are not mutually exclusive.

Whether a modify is a retract+assert of the entire fact,  a 
retract+assert of triples representing those change, a single 
propagation of the entire fact or a single propagation of the triples 
representing those changes is I believe an implementation detail.

As mentioned previously I think refraction should be an optional part of 
the spec. With OPS5 implementing it (the grand daddy of PRDS) and OPSJ 
and JRules I think there is enough justification that this is not an 
esoteric feature.

I would like to see some variation of slot-specific included in the 
spec, but I'll leave out the details for what this should look like for 
another discussion. But I believe it, like refraction,  should be 
optional behaviour and again independant of how the modify is actually 
implemented.

As long as we have a modification action that includes the list of 
changes in the spec, slot specific can be easily added at a later date.

Mark
>
> We need to consider some test cases to be sure we are all talking 
> about the same thing. Here is a variation of a no-loop test. I think 
> this should never loop (we should not pick a semantics that causes 
> this to loop):
>
> Document(
> Prefix(ex <http://example.org/example#>)
> Prefix(func <http://www.w3.org/2007/rif-builtin-function#>)
> Prefix(pred <http://www.w3.org/2007/rif-builtin-predicate#>)
>
> Group (
> Forall ?X ?C1
> If
> And( ?X[ex:count1 -> ?C1] pred:numeric-greater-than(?C1 0) )
> Then Do (
> (?C2 (?X[ex:count2 -> ?C2]))
> Modify (?X[ex:count2-> func:numeric-subtract(?C2 1)])
> )
> )
>
> ex:foo[ex:count1 -> 10 ex:count2->10]
>
> )
> )
>
> The above entails
> ex:foo[ex:count1 -> 10 ex:count2->9]
> but does NOT entail
> ex:foo[ex:count1 -> 10 ex:count2->8]
>
> Christian De Sainte Marie wrote:
>>
>> All,
>>
>> csma wrote on 18/01/2010 15:43:48:
>> >
>> > [...]
>> >
>> > I started modifying the spec tentatively along these lines, in case
>> > we would agree that the proposed changes are needed, and that they
>> > are correct.
>>
>> I finished the tentative modifications for point 1 (taking 
>> intermediate states into account) and 3 (taking the matched facts 
>> into account in the characterisation of a rule instance).
>>
>> I reversed to the published version before doing the modification 
>> (thus rolling back some other tentative modifications I had made in 
>> between). To find the modifications, you have to compare with 
>> Sandro's version from October 1 [1]. Notice that I re-ordered the 
>> definitions somewhat, to improve readibility (that is, there are less 
>> modifications, really, than the comparison shows :-)
>>
>> [1] 
>> http://www.w3.org/2005/rules/wiki/index.php?title=PRD&diff=11952&oldid=11437 
>> <http://www.w3.org/2005/rules/wiki/index.php?title=PRD&diff=11952&oldid=11437> 
>>
>>
>> I did do any modification wrt the Modify issue, yet (since one 
>> possibility is to, simply, remove it :-)
>>
>> Cheers,
>>
>> Christian
>>
>> IBM
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>>
>>
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>>
>
Received on Tuesday, 3 August 2010 09:50:37 GMT

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