[rules-users] Anti-rules and infinate loops

[Michael Neale]

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 at 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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