[rules-users] multi-factor rule

[Welsh, Armand]

Try this:

rule 'Rule One'
activation-group 'age-test'
salience 300
when
	Person (location == 'A',  age > 60 )
Then
	do_something();
end

rule 'Rule Two'
activation-group 'age-test'
salience 200
when
	Person (location == 'B',  age > 70 )
Then
	do_something();
end

rule 'Rule Three'
activation-group 'age-test'
salience 100
when
	Person (location == 'C',  age > 80 )
Then
	do_something();
end

rule 'Rule Else'
activation-group 'age-test'
when
	Person (age > 65 )
Then
	do_something();
end


This will do what you want, and the first rule that matches will cancel the activation of any other rules that matches.  However, because these rules are not mutually exclusive,  this is not the best way to represent the logic, since a change to person could cause the wrong rule to fire, since only the rules that are affected by the change would be re-activated.

The EASIEST way to represent this is with an Excel Spreadsheet (or the Guvnor Decision Table).  Then you can craft the table to identify each rule exclusively, and use the otherwise keyword to deal with the negation of all specified facts.  If you can represent your rules without requiring salience as the conflict resolver, then you will have better (more predictable) rules, since this would mean that only one of the group rules could ever be true at any instance in proessing.



-----Original Message-----

> ronalbury wrote
>> Hi - I am a Drools newbie and I apologize in advance if the answer to my
>> question is intuitively obvious to the casual user.
>>
>> I have an object that has two fields: location(there are more than 50
>> locations) and age.  I am having difficulty building clean rules for the
>> following pseudo-code
>>
>>
>> // Rule One
>> if(location == "A") {
>>     if(age>  60)
>>        do_something();
>> }
>> // Rule Two
>> else if(location == "B") {
>>      if(age>  70)
>>          do_something();
>> }
>> // Rule Three
>> else if(location == "C") {
>>      if(age>  80)
>>          do_something();
>> }
>> // Rule Four
>> else {
>>      if(age>  65)
>>          do_something();
>> }
>>
>> The issue comes with Rule Four.  How do I avoid writing the rule so that I
>> don't have to say (location!="A"&&location!="B"&&location!="C") ?  I also
>> don't want to have to write an explicit rule for every possible location.
>>
>> I considered an activation-group with salience to have the rules executed
>> in order, but the problem is that if rules 1-3 do not fire, then rule 4
>> fires for all locations - I can get a hit if location=="C" and age==70.
>>
>> Is it possible to have a 'Map' and do something like
>> (age>map.get(location)) ?  I could live with creating a map with all
>> possible locations for key, although I'd rather not go this route.
>>
>> This problem is typical for the types of rules I'll be writing ... there
>> can be completely different sets of rule criteria depending on location.
>>
>>
>> Thanks in advance for your suggestions and your patience.
>>
>> _______________________________________________
>> rules-users mailing list
>> rules-users at .jboss
>> https://lists.jboss.org/mailman/listinfo/rules-users
>>
>
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