here is the rule that will work:
(defrule items-to-buy
?ItemFound <- (SomethingIWant (Name ?ItemName)
(Price ?ItemPrice)
(Priority ?ItemPriority1)
(Selected false ) )
(not (SomethingIWant (Selected false) (Priority ?p&:(< ?p ?ItemPriority1))))
=>
(printout t "Found: " ?ItemName ", " ?ItemPrice ", " ?ItemPriority1 crlf)
(modify ?ItemFound (Selected true) )
)
In addition you should execute (run) at the end of the file, or from JESS prompt
Dusan Sormaz
PS. If you see smiley in (not ...) clause replace it by : ( .
At 09:30 PM 2/13/2006, you wrote:
OK, Im very, very new to JESS and rules engines, so please forgive me for a very basic question. I have read JESS in Action but Im still stumped on this one. I get that the rules engine will match all possible facts against my rule(s). I think of it as kind of an implied iteration, versus a loop in a procedural language. But, Id like to have some control over the order in which those facts are applied to my rule. For example, imagine I have a database of stuff on my wish list. I keep the name of each item and the price. And I have a rule that will match on all of the entries in the database, and do something like make a shopping list and keep a running total. So far, so good. But, I have a limited budget, and an infinite wish list. So, I want to make sure my rule matches the things I want the most, first. And this is where Im stuck. I can add a Priority slot. But, how do I write the rule to match on the higher priority facts, first? I played with a (not ) statement I saw in JESS in Action, but it doesnt quite do what Im looking for. I may have 3 priority 1 items and Ill want the rule to match on all of them, and I might have 2 priority 2 items and Ill want to rule to match on both of those. But, I want the rule to match on all of the priority 1 items before any of the priority 2 items. I pasted my test code below. Im sure I just havent gotten my mind wrapped around how you do things in this environment, yet. But, I could use a nudge in the right direction on this one. Thanks in advance for any suggestions!
Eric
; Test Prioritizing Facts.
(printout t crlf crlf)
(clear)
(reset)
(deftemplate SomethingIWant "Stuff I want"
(slot Name (default Whatever) )
(slot Price (default 10) )
(slot Priority (default 0) )
(slot Selected (default false) )
)
(assert
(SomethingIWant
(Name "TiVo")
(Price 200)
(Priority 1)
)
)
(assert
(SomethingIWant
(Name "DVD Burner")
(Price 400)
(Priority 5)
)
)
(assert
(SomethingIWant
(Name "Wheels")
(Price 1000)
(Priority 2)
)
)
(defrule items-to-buy
?ItemFound <- (SomethingIWant (Name ?ItemName)
(Price ?ItemPrice)
(Priority ?ItemPriority1)
(Selected false ) )
?ItemFound2 <- (SomethingIWant (Name ?ItemName2)
(Price ?ItemPrice2)
(Priority ?ItemPriority2) )
; (not (eq ?ItemName ?ItemName2 ) )
(not (SomethingIWant (Priority ?ItemPriority2&:(> ?ItemPriority1 ?ItemPriority2 ))))
; (test (<= ?ItemPriority1 ?ItemPriority2 ) )
=>
(printout t "Found: " ?ItemName ", " ?ItemPrice ", " ?ItemPriority1 crlf)
(modify ?ItemFound (Selected true) )
)
* Duan ormaz, PhD, Associate Professor
* Ohio University
* Industrial and Manufacturing Systems Engineering Department
* 277 Stocker Center, Athens, OH 45701-2979
* phone: (740) 593-1545
* fax: (740) 593-0778
* e-mail: [EMAIL PROTECTED]
* url: http://www.ent.ohiou.edu/~sormaz
*********************************************************************
