[rules-users] Fact Execution Order

[Wolfgang Laun]

An array and an ArrayList may or may not associate a meaning with the order
of elements,
or even with the array index, e.g., if the index is a month's number (-1).

If your facts MyFact need to reflect this order or even the index number,
you ought to add this
as an attribute to MyFact, and storing these objects in destination[] should
use this index attribute.

I would not rely on any evaluation order of rules, or try to influence rule
firing so that it
maintains order.

-W

On Mon, Jan 4, 2010 at 7:37 PM, Nawrocki, Dan (IS)
<Daniel.Nawrocki at ngc.com>wrote:

> I want to control the order of firing for facts that match a single
> rule.  I'm using Drools 5.0.1.  Is there any way to do this?
>
> My problem can be boiled down as follows.  I have an array structure
> that I want to conditionally copy to a new array structure.  I would
> like to order of the destination array to match the source array.  The
> code to insert facts into working memory increments in ascending order.
> It is equivalent to:
>
> for( Object o : sourceArray )
>  ksess.insert( convertToMyFact( o ) );
>
> I have constructed my rules as such:
>
> rule "rule1"
> when
>   $f : MyFact( prop == "testVal" )
> then
>   copyToDestination( $f.prop, $f.index );
> end
>
> After running, however, the destination array appears in reverse order:
> source[0] == destination[5]
> source[1] == destination[4]
> source[2] == destination[3]
> source[3] == destination[2]
> source[4] == destination[1]
> source[5] == destination[0]
>
> Which seems to make sense if the facts are evaluated as if they were
> popped off a stack.  Is there any way to force Drools to use a list
> instead?  Or should I just insert facts in reverse order?
>
> I would like the order:
> source[0] == destination[0]
> source[1] == destination[1]
> etc.
>
> Thanks,
> Dan
>
>
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