RE: [TED] CORE Pages on Positive Conditions and Horn Rules Edited:Slots & Constraints

Slots and Constraints can be separated, as shown in my other email
(http://lists.w3.org/Archives/Public/public-rif-wg/2006Nov/0082.html).
However, slotted syntax has been mandated by the Charter 2.2.4, and
already the condition language, introducing Expressions and Atoms,
can benefit from slotted versions of these forms in queries etc.
Because of the extensible design, rules then inherit the ensuing
slotted conditions.
On top of that, rules can also be given the optional constraint part
asked for in slide 5: (Forall) H :- B1, ..., Bm [ &  C]

On the other hand, we could keep the condition language unchangeed,
only extending the rule language with the optional constraint part.
Example 3b' (of http://www.w3.org/2005/rules/wg/wiki/B.1_Horn_Rules)
happens to be of that kind, since slots don't seem to be crucial for
its unary and binary relations (and ternary built-in-like timediff):

  Forall ?agent ?item ?deliverydate ?scheduledate ?diffdate
        (
          reject(?agent ?item) :-
             And ( perishable(?item)
                   delivered(?item ?deliverydate)
                   scheduled(?item ?scheduledate) )
             &
             And ( ?agent=John
                    timediff(?diffdate ?deliverydate ?scheduledate)
                    greaterThan(?diffdate 10) )
        )

The only fixed arg, John, of the earlier "reject(John ?item) :- ..."
version is handled by the first constraint, ?agent=John, here.

In a fully modular design, we can introduce both extensions in an
independent manner, as separate dialects, yet bring them together
again in a combined extension dialect.

-- Harold


-----Original Message-----
From: cawelty@frontiernet.net [mailto:cawelty@frontiernet.net] 
Sent: Monday, November 20, 2006 12:52 PM
To: Boley, Harold
Cc: RIF WG
Subject: Re: [TED] CORE Pages on Positive Conditions and Horn Rules
Edited:Slots & Constraints

Quoting "Boley, Harold" <Harold.Boley@nrc-cnrc.gc.ca>:

>
> Referring to the slides of an F2F4 breakout session
> (http://lists.w3.org/Archives/Public/public-rif-wg/2006Nov/0025.html),
> I edited two wiki pages for extending the existing work with
> slots and calls to external constraint solvers (ACTION-180):

What you have proposed doesn't match my own understanding of what we  
discussed at the breakout.  My understanding was that the condition  
language wouldn't change, just that for *rules* constraints would be  
added (so head, body, vars, and constraints would be the parts of a  
rule) and for the core the constraints would be limited to identity  
constraints that woudl bind variables in the rule.  So handling  of  
keyword args would be in the constraints.

This would be much easier (for me) to describe, explain, and discuss  
at an abstract syntax or meta-model level.  It is really difficult  
(for me) to understand the changes to the syntax by reading the eBNF.

-Chris


>
>
> Slots (CORE Page on Positive Conditions):
>
> http://www.w3.org/2005/rules/wg/wiki/A.1_Basis%3A_Positive_Conditions
>
>
http://www.w3.org/2005/rules/wg/wiki/A.1_Basis%3A_Positive_Conditions?ac
> tion=diff&rev2=45&rev1=43
>
>
> Calls to external constraint solvers (CORE Page on Horn Rules):
>
> http://www.w3.org/2005/rules/wg/wiki/B.1_Horn_Rules
>
>
http://www.w3.org/2005/rules/wg/wiki/B.1_Horn_Rules?action=diff&rev2=24&
> rev1=22
>
>
> Further edits, for corresponding extensions of the DTDs and
> SEMANTICS sections, are in preparation.
>
> -- Harold
>
>

Received on Tuesday, 21 November 2006 06:19:54 UTC