[rules-users] exists + normal column constraints - how many t imes a rule is cal led in the end????

[Olenin, Vladimir (MOH)]

Thanks, Oana. I think I'm finally starting to get a grip on this thing :-).

 

 

Vlad

 

 

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From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at lists.jboss.org] On Behalf Of nicolae oana
Sent: 20 February 2007 03:38
To: Rules Users List
Subject: Re: [rules-users] exists + normal column constraints - how many
times a rule is cal led in the end????

 

Vlad,

exists Person(role == "parent")  

checks if in workingMemory is at least one Person fact having  attribute
role == "parent", in both your examples.

Your reasoning is correct: the four facts with role =="child" will activate
the rule. So, the result for your second example will be the same as the
first result, for your list of facts, no matter how you switch the columns.

Regards,
             Oana

"Olenin, Vladimir (MOH)" <Vladimir.Olenin at moh.gov.on.ca> wrote:

Hi,

 

I'm not sure my understanding of 'existential quantifiers' is correct.
Hopefully, someone can clear it up a bit...

 

Providing I have the following fact class:

 

Person(role: parent/child, name)

 

And following facts:

 

1: parent, John

2: parent, Alice

3: parent, Steve

4: parent, Jane

5: child, Eric

6: child, Rob

7: child, May

8: child, April

 

I expect the rule

 

Rule "iterate children if at least one parent is found"

When

            exists Person(role == 'parent')

            $child: Person(role == 'child')

Then

            // do smth for each $child if at least one parent is found

End

 

 

To iterate through all 'child' persons (facts 5 through 8), ie the action
will be called exactly 4 times. Is this correct? What would happen if I swap
the order of the conditions (with 'parent exists' constrain going _after_
'child' constraint):

 

When

            $child: Person(role == 'child')

            exists Person(role == 'parent')

 

Thanks,

 

Vlad

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