On Jan 24, 2007, at 9:15 PM, [EMAIL PROTECTED] wrote:
I
only include their numbers because I believe that is all that is
important
- maybe that is my problem
Indeed. In OPS5 and in systems like CLIPS, the fact number is
directly related to the recency of a fact. If you modify a fact in
CLIPS, the old fact is removed and a new one, with a new fact number,
is asserted.
Jess has a more object-oriented approach; a fact's fact number is a
constant and doesn't change when the fact is modified. This lets you
use those IDs as links between facts that survive property
modifications. Therefore there isn't necessarily any relationship
between the recency of a fact and the fact number. Each fact contains
a "pseudo-time" value, basically a tag that identifies the order of
events that happen in the engine. The agenda ordering is based on
these pseudo-time tags. The default strategy is called "depth", and
it orders activations according to the recency of their facts,
weighted so that activations that include more facts are given some
preference.
---------------------------------------------------------
Ernest Friedman-Hill
Advanced Software Research Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://www.jessrules.com
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