The agent that is responsible for the address change must take care to provide information about what it does. This could be done by creating an UpdateEvent fact referencing the Person fact and indicating the attribute (address). Or a listener reacts to the change and insert the UpdateEvent fact.

Or you follow your "ideally-we-should-have-2" idea.

-W



On 9 November 2011 09:29, kapokfly <ivan.jiang.ww@foxmail.com> wrote:
Requirement:

1)
    Rule
    When
        Person.address.address1 is changed
    THEN

2) Ideally we should have 2 objects, 1 for the old person instance, the
other for the new person instance so contextually the LHS equals to
oldPerson.address.address1 != newPerson.address.address1.

A properties change listener might not be the best solution as it might span
multiple calls and the property change could be done on the web layer which
is out of the JBoss Drools knowledge session.

Ivan

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