[drools-user] How do I control firing of rules ?

[Ho, Alan]

Hi,

I'm fairly new to drools, and was curious if there is a way to reduce the 
firing of rules.

Whenever a fact is modified, drools fires all rules who's parameter ( is the 
same class type of the fact. 

e. g. 

    <rule name="Order Level" salience="1" >
        <parameter identifier="order">
            <class>com.blah.shipping.ruleengine.Order</class>
        </parameter >
        <parameter identifier="item">
            <class>com.blah.shipping.ruleengine.Item</class>
        </parameter >
     :
     :
     :
    </rule>
       
Whenever we modify any fact of type object Item or type Order, this above rule 
will fire.


Can we somehow specify a parameter based a sub-field of an object. Something 
like

    <rule name="Order Level" salience="1" >
        <parameter identifier="order">
            <class>com.blah.shipping.ruleengine.Order</class>
        </parameter >
        <parameter identifier="Item">
            <instance>order.orderItem</instance>
        </parameter >
     :
     :
     :
    </rule>

Where order.orderItem is of type Item. In this scenario, the rule will only 
fire when an order fact or order.orderItem is modifed. 

Right now, to emulate the behaviour I am looking for, I am doing a check in a 
rule condition:


    <rule name="Order Level" salience="1" >
        <parameter identifier="order">
            <class>com.blah.shipping.ruleengine.Order</class>
        </parameter >
        <parameter identifier="item">
            <class>com.blah.shipping.ruleengine.Item</class>
        </parameter >

        <java:condition>order.orderItem == item</java:condition>

     :
     :
     :
    </rule>

Thanks,
Alan Ho