If you don't have some way of associating the data with a particular Latch it's
easy to get overlap when processing datasets. In general you need some way to group the
data together. You can avoid a back reference to the Latch by having a Set of some sort
in the Latch to which you add all data in the batch. If you use a Set backed by an
IdentityHashMap the overhead is pretty small, and rules look like this:
rule "CountAs"
dialect "java"
salience -1
when
l : Latch()
a : A( this memberOf l.dataSet )
then
retract(a);
l.incACount();
System.out.println("Found an A in " + l);
end
See attached project.
THough I like the cleverness of using the "data in matched objects alters rule
properties" trick, you could have just as easily had a "Latch(value ==
true)" conditional, and that would be more clear, IMO. I'm curious to see of the
enabled trick would perform better, though.
GreG
--- On Sun, 10/3/10, Wolfgang Laun <wolfgang.laun(a)gmail.com> wrote:
From: Wolfgang Laun <wolfgang.laun(a)gmail.com
Subject:
Re: [rules-users] fireUntilHalt and timing of rule activations
To: "Rules Users List" <rules-users(a)lists.jboss.org
Date: Sunday, October 3, 2010, 4:23 AM
There is another way of associating a Latch object with rules, without having to store a
reference to a Latch in objects:
rule "CountAs"
enabled ( $v )
when
Latch( $v : value )
X( ... )
then ... end
At the beginning, insert Latch( false ), which blocks all rules with this construction, or
modify the Latch object to false before inserting more facts. Then, insert the facts, and,
at the end, modify Latch to true.
Latch latch = new Latch( true );
FactHandle fh = kSession.insert( latch );
kSession.fireAllRules();
latch.setValue( false );
kSession.update( fh, latch );
Of course, you can use multiple Latch objects, adding a name field with a specific value,
so that a latch applies to a subset of rules only:
rule "CountAs"
enabled ( $v )
when
Latch( name == "CountAs", $v : value )
...
But be aware that changes to Latch objects will retrigger rules that have fired
previously; so with this approach you'll have to make sure to retract facts when they
have been processed.
-W
2010/10/3 Greg Barton <greg_barton(a)yahoo.com
Nope, you're not missing anything. What you need is a control object of some sort
thst's inserted after all of the "real" data is inserted. (See attached
project for an example.) Rules will look like this, if the control object is called
BatchLatch and data objects A:
rule "CountAs"
dialect "java"
salience -1
when
l : Latch()
a : A( latch == l )
then
retract(a);
l.incACount();
System.out.println("Found an A in " + bl);
end
Note that the A object being processed is tied back to the latch. This is so multiple
latches can be processed simultaneously and their processing won't be intermingled.
This is necessary because there's no guarantee that two Latch objects aren't in
working memory at once. (Though you could create a rule that enforces this.)
GreG
--- On Sat, 10/2/10, Norman C <rent_my_time(a)yahoo.com> wrote:
From: Norman C <rent_my_time(a)yahoo.com>
Subject: [rules-users] fireUntilHalt and timing of rule activations
To: rules-users(a)lists.jboss.org
Date: Saturday, October 2, 2010, 10:22 AM
Hi All,
In my app, I have a separate thread calling fireUntilHalt()
continuously. I
have quite a few rules, and I am using salience extensively
to control the order
in which rules are executed. What I have seen (by adding
an event listener) is
that as a new fact is inserted, various rules are
activated. Often, the
fireUntilHalt will start executing fireNextItem in
DefaultAgenda before all of
the activations are complete. So if the rule with the
highest salience
value hasn't been activated at this point, then the first
rule to be fired isn't
the correct one.
This can be worked around by waiting for insert to return
and then calling
fireAllRules(). But it seems like the session should
block fireUntilHalt from
trying to execute activated rules until all activations are
complete. Or am I
missing something here?
thanks,
Norman
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