I think Greg Biegel wrote:
> And I have the following rule:
>
> (defrule InUse-BottomLeft
> ?ac <- (active-context InUse)
> ?cu <- (context-updated true)
> (and
> (and
> (LoadCellSensor1_MassEvent_Bean (sensorID 1))
> (LoadCellSensor1_MassEvent_Bean (mass ?LoadCellSensor1_MassEvent&:(>
> ?LoadCellSensor1_MassEvent ?*averageweight*)))
> )
...
Two comments. First, regarding writing rules efficiently: you can, and
most certainly should, match multiple slots in a single pattern. Using
multiple patterns this way consumes more memory and does more
computational work (and of course, if there were more than one
LoadCellSensor1_MassEvent_Bean object, then the above would match all
the possible permutations of matches based only on single-slot
matching, which I'm sure you wouldn't want. Also, there's an implicit
"and" around the whole LHS of a rule, and furthermore, an "and" inside
an "and" is just extra work for the parser, as (and (and X Y) (and P
Q)) is precisely equivalent in meaning to (and X Y P Q). So drop all
the "and"s, combine the multiple patterns, and just write:
(defrule InUse-BottomLeft
?ac <- (active-context InUse)
?cu <- (context-updated true)
(LoadCellSensor1_MassEvent_Bean
(sensorID 1)
(mass ?mass1&:(> ?mass1 ?*averageweight*)))
I picked a shorter variable name for you, too.
Secondly, pattern-matching is driven by fact assertions,
modifications, and deletions; as you observed, if you match with a
global variable, the matches won't be updated until the facts are
modified. From the end of section 2.8.2 of the manual:
"If you match to a defglobal with a pattern like (foo ?*x*), the match
will only consider the value of the defglobal when the fact is
asserted. Subsequent changes to the defglobal's value will not
invalidate the match - i.e., the match does not reflect the current
value of the defglobal, but only the value at the time the matching
fact was asserted."
If you need matches to respond to changes in the average weight in
real time, then simply store the average weight in a fact (or a
dynamic definstance) rather than in a defglobal.
---------------------------------------------------------
Ernest Friedman-Hill
Science and Engineering PSEs Phone: (925) 294-2154
Sandia National Labs FAX: (925) 294-2234
PO Box 969, MS 9012 [EMAIL PROTECTED]
Livermore, CA 94550 http://herzberg.ca.sandia.gov
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