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Re: [PRD] ACTION-434: new PRD draft is out

From: Gary Hallmark <gary.hallmark@oracle.com>
Date: Wed, 21 May 2008 16:46:24 -0700
Message-ID: <4834B450.3010109@oracle.com>
To: Christian de Sainte Marie <csma@ilog.fr>
CC: RIF WG <public-rif-wg@w3.org>


This is a much improved version!


I continue to note the difference in presentation style in PRD vs BLD:
BLD starts with PS syntax and then "derives" the XML from the PS.
PRD, on the other hand, starts with XML and "derives" the PS.
Much like choosing to drive on the right vs. the left side of the road, 
the initial choice is somewhat arbitrary -- but once chosen, it is good 
for others to adopt a consistent practice!

I have implemented a prototype translator from OBR (production rules) to 
BLD  [1].  I am able to translate the 2 rules from Use Case 1 (reworked 
slightly to convert relations to frames).  The translation effectively 
translates an "assert new frame" action and an "assert (set) property of 
existing frame" action to a BLD rules.  I would like the syntax of the 
RIF rules to be exactly the same, whether I am in the BLD dialect or the 
PRD dialect (because as far as I can tell, the semantics are the same).  
That way, my RIF document can be of use to the widest audience, and I 
don't need multiple translations depending on the consumer (I may post 
the rules on a web page and not even know who the consumer is)

So, let's reuse the Implies and Forall from BLD and get rid of 
ConditionalStatement and Pattern. Extend the "then" part of Implies to 
include retract/remove and possibly other actions (but allow ATOMIC and 
not require Assert).  Also, the ATOMIC needs to support the skolem 
function "rif:new" to allow "creating" a new frame instance.

I like the fanciful example with chickens and mashed potatoes, but it 
would be good to use examples from the use cases (maybe the fanciful 
example should be added).  At least one example (e.g. use case 1) should 
be shown in both BLD and PRD and should only have to be shown once 
because the PS and XML syntax should be identical.

The xml just before 2.3.2 contains curies like jim:today -- is this 
legal or must the full IRI be used?


I think we are getting close to the point where we can argue about the 
semantics of our rule engines by relating then to this model, rather 
than arguing about the model itself.  Very good!

There are some issues with your symbols.  They don't all render on IE.  
Upper-case Gamma isn't very mnemonic for Configuration (ok, they both 
start with the 3rd letter in some alphabet).  Why use L for the set of 
actions but alpha for an element of the set?  Suggestion: use the Latin 
alphabet, e.g. C, c, A, a

The phrase "as usual" is annoying because I can't check if it is "usual" 
because your reference links aren't working.

Sometimes in your semantic formulas you use ?x and other times just x 
for quantified variables.  I find ?x distracting following an upside 
down A or backward E.

3.3 semantics for actions

In [1] I translate the action to assert a new frame of type T and set 
its "id" property to some value as:
And( rif:new(T,?id)#T rif:new(T,?id)[id->?id] )
(In BLD, we have to split this into "then" into 2 rules to remove the And)
Can we interpret this as adding 2 ground terms to W?

3.4.3 halting

as I understand it, the following ruleset

Forall ?x (o[y->?x] :- o[x->?x])

would never halt with your proposed default because the condition is 
always true.  I think the default should be some kind of fixpoint (i.e. 
when w' = w)

Other halting policies:
- rules can fire at most once (I've heard biztalk does this; also PRR's 
sequential mode)
- no rule can cause itself to re-fire (OBR and Jess have a per-rule 
declaration for this)
Can we express these in your formalism?

More later...

[1] http://lists.w3.org/Archives/Public/public-rif-wg/2008May/0126.html

Christian de Sainte Marie wrote:
> All,
> I just finished a new version of the PRD draft [1], based on the 
> reviews of the previous draft and the following discussions at F2F9.
> As I may continue working on the incomplete sections at the end of the 
> draft between now and the F2F, Sandro made a snapshot, for review 
> before F2F10, with the objective of publishing a 1st public WD:
> http://www.w3.org/2005/rules/wg/draft/rif-prd/
> Comments, opinions, suggestions for improvements etc are welcome, as 
> usual.
> This completes my action-434: New PRD draft reflecting F2F9 PRD 
> break-out discussion.
> Christian
> [1] http://www.w3.org/2005/rules/wiki/PRD
Received on Wednesday, 21 May 2008 23:47:58 UTC

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