4:14 p.m.
Hello,
I have a set of rules that determine a target date for a business object
based on which rule criteria the object matches. When the business
object is asserted, the target date field may or may not be null. My
problem is if the business object does not match any of the rules I
would like the target date set to null and since there are multiple rule
possibly affecting the same object I would rather not create an
"anti-rule" for each rule which sets the target date to null.
I've tried creating a rule with a higher salience value which sets the
target date to null, if it is not already, and modifies the object but
when the object matches another rule and modifies the object again it
goes into an infinite loop. I could probably set the target date to
null before asserting it into the rule engine but I was hoping to keep
it self contained.
Here's an example of what I'm talking about:
rule "Pre"
salience 10
no-loop true
when
$bo : MyObject( targetDate != null )
then
Date tmp = null;
$bo.setTargetDate(tmp);
modify($bo);
end
rule "Post a"
no-loop true
when
$bo : MyObject( targetDate == null, criteriaMatches == "A")
$someDate : ThisDateObject();
then
$bo.setTargetDate($someDate);
modify($bo);
end
rule "Post b"
no-loop true
when
$bo : MyObject( targetDate == null, criteriaMatches == "B" )
$someDate : ThatDateObject();
then
$bo.setTargetDate($someDate);
modify($bo);
end
etc...
I'm pretty sure there is a simple answer but it just won't come to me.
Thanks for any help.
Myles
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5:33 p.m.
One way around this is to set the high-salience "default" rule to also
trigger on the non-existence of some "marker" object. Then, in the
consequence, you can always assert a new instance of that object, which then
effectively blocks the rule from triggering again. If you want it to
automatically manage itself, you may be able to do an assertLogical on the
marker object and then it will get removed when the business object gets
retracted.
So, something like this maybe:
rule "Pre"
salience 10
when
$bo: BusinessObject(targetDate != null)
!Marker()
then
assertLogical(new Marker());
Date tmp = null;
$bo.setTargetDate(tmp);
modify($bo);
end
I've had to do that sort of stuff before to handle edge cases like this.
--- Michael
4:01 a.m.
Thats a clever suggestion,
Another way (more brute force procedural), is to use agenda-groups.
So most of your rules are in an agenda-group called "calculateDate" or
similar.
You then have a group called "deftault" which just has the rule that checks
if the date is still null, and sets it.
You then (from the api) do
workingMemory.setFocus("calculateDate");
workingMemory.setFocus("default");
workingMemory.fireAllRules();
or similar.
In the next release, we are looking at including an "Otherwise()"
functionality for this, so you have a rule that declares that it will fire
only if no other rules did.
I have a prototype implementation of that in trunk.
So lots of options, I think the agenda group may be a little too verbose
though, I liked Michael's suggestion in a previous email.
Michael.
On 1/9/07, Michael Suzio <msuzio(a)gmail.com> wrote:
One way around this is to set the high-salience "default" rule to also
trigger on the non-existence of some "marker" object. Then, in the
consequence, you can always assert a new instance of that object, which then
effectively blocks the rule from triggering again. If you want it to
automatically manage itself, you may be able to do an assertLogical on the
marker object and then it will get removed when the business object gets
retracted.
So, something like this maybe:
rule "Pre"
salience 10
when
$bo: BusinessObject(targetDate != null)
!Marker()
then
assertLogical(new Marker());
Date tmp = null;
$bo.setTargetDate(tmp);
modify($bo);
end
I've had to do that sort of stuff before to handle edge cases like this.
--- Michael
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2 comments
3 participants
participants (3)
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Michael Neale -
Michael Suzio -
Myles Goodhue