[rules-users] persistent java objects in working memory

[Chris Richmond]

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

 

  _____  

From: rules-users-bounces at lists.jboss.org
[mailto:rules-users-bounces at 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.

  _____  

From: Chris Richmond <crichmond at referentia.com>
To: Rules Users List <rules-users at 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

 

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