I think Conor Power wrote:
>
> Hi,
> I have a question regarding how to use the attribute
> of a java object in the LHS of a rule.
>
...
> I want a rule to fire depending on the value of the cmp member variable
>
> I envisage using something like follows
>
> (defrule r1
> (get ?*x* cmp)
> =>
> (DO SOMETHING)
> )
>
> Is this okay??
No - the things on the left side of a rule are always patterns, never
function calls. WHaqt you've written would match a fact with the head
'get' and two fields with the given values.
>
> The next problem I have is that, I set the member variable cmp in the
> right side
> of another rule. In this situation will the above rule check (get) the
> new value and
> test it. Do I need to add "notify changed" functions to the Foo object?
>
> Is my methodology correct?
You can only match properties of Java Beans on rule LHSs. The Beans
must have propertyChangeListener support. Study the
jess/examples/pumps/ example to learn the details.
The reason for this is simple, and I think you have an inkling of it
here: Jess has to have some way of knowing when a property's value
changes, or else it couldn't use the Rete algorithm to match the
property: it would have to poll it, I suppose, which would be silly.
---------------------------------------------------------
Ernest Friedman-Hill
Distributed Systems Research Phone: (510) 294-2154
Sandia National Labs FAX: (510) 294-2234
Org. 8920, MS 9214 [EMAIL PROTECTED]
PO Box 969 http://herzberg.ca.sandia.gov
Livermore, CA 94550
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