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[PRD] [Core] variable binding restriction in PRD

From: Gary Hallmark <gary.hallmark@oracle.com>
Date: Mon, 22 Sep 2008 13:01:55 -0700
Message-ID: <48D7F9B3.1080503@oracle.com>
To: rif WG <public-rif-wg@w3.org>

As shown in [1] and [2], forward (backward) chaining systems may have 
trouble if variables are bound to predicates/frames in the head (body) 
of a rule.

So for Core, we have to decide whether one style is preferred to the other.

I know that in most PR systems, all variables must be bound to 
predicates or frames in the condition.  We need a "PRD Core" that 
defines a subset of PRD where all variables are bound to predicates or 
frames in the condition. This will allow a PRD translator to be 
implemented without the burden of equation solving for the 
frame/predicate variables in body should you receive a rule in which 
they are bound in the head  Is this too onerous for Core?  I imagine 
that a "BLD Core" would want just the reverse: all variables are bound 
to predicates or frames in the head.

[1] http://www.w3.org/2005/rules/wiki/Chaining_strategy_numeric-subtract_1
[2] http://www.w3.org/2005/rules/wiki/Chaining_strategy_numeric-add_1
Received on Monday, 22 September 2008 20:03:42 GMT

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