Well my little test seems to confirm that this does indeed work, although I am not clear as to exactly why?

Also, how do I prevent modifications made to a MyObject in another rule from making this one fire again?  Can I do it by always having this one with the highest salience to ensure it runs first?  Or would it be preferable to set a “dirty” flag on the object and make this rule make sure that hasn’t been checked.   That might not be an option an an object you can’t mofidy for specific rule engine usage.

Thanks,

Chris

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From: rules-users-bounces@lists.jboss.org [mailto:rules-users-bounces@lists.jboss.org] On Behalf Of Greg Barton
Sent: Wednesday, September 23, 2009 10:02 AM
To: Rules Users List
Subject: Re: [rules-users] persistent java objects in working memory

You've answered your own question. :)  The rule you've given will only fire when the object is asserted or modified. (And you have to inform the engine of the modification.)  You have to inform the engine that the object has been modified every cycle. (And if you want the engine to fire that rule even if the object has not been modified, you can still inform the engine.  All that does is force the rules to reconsider the object.)

However, the way I'd do it is to have a new object that is inserted on each iteration.  Let's call it "Cycle" and give it a count. Then your rule would look like this:

rule "Identify Java Objects"

   lock-on-active

when

   $mo : MyDataObject();

   $c : Cycle();

then

   System.err.println("MYOBJECT in system: " + $mo.getID() + " | " + $mo.getTestFieldData() + " on Cycle " + $c.getCount());

end

When the iteration is over, you would retract the Cycle object.  (Only one Cycle should be in working memory at once, and it's a good idea to have a rule that enforces that invariant.)  You should follow this pattern for any rule you want to guarantee to fire on each iteration.

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From: Chris Richmond <crichmond@referentia.com>
To: Rules Users List <rules-users@lists.jboss.org>
Sent: Wednesday, September 23, 2009 2:15:35 PM
Subject: [rules-users] persistent java objects in working memory

Hello,

I am trying to create a set of java objects, which I insert into the session at startup.  Then at regular timed iterations I want to examine the values of those objects.  During the timer iteration, some fields may have been changed by the primary program.  So I have a rule for now that is just trying to identify that the do indeed exist on each iteration:

rule "Identify Java Objects"

   lock-on-active

when

   $mo : MyDataObject();

then

   System.err.println("MYOBJECT in system: " + $mo.getID + " | " + $mo.getTestFieldData);

end  

As I said, at startup I insert 3 of these objects into my session, then every 10 seconds I just want to ensure they are there.  However the output from this rule only fires on the firet iteration, after that the rule doesn’t fire.  I am not retrcating the objects or even concerning myself with the FactHandle, as I plan to leave them in working memory and change values on those 3 objects from the main application in each application loop, then make decisions in the rule engine based on the values of those 3 objects.   However, for now I just nee to find out why the objects only live for my first loop and call of session.fireAllRules().

Any ideas or what I am doing wrong?

Thanks,

Chris