2009/11/26 Leonardo Gomes <leonardo.f.gomes@gmail.com>

On Tue, Nov 24, 2009 at 10:42 PM, Leonardo Gomes <leonardo.f.gomes@gmail.com> wrote:
Now, let's say FactA(1) indicates a fact of type FactA and id = 1.

- Then, in the beginning, I insert FactA(1) and FactA(2) in my working memory and fire the rules.

rule "test non existence"
    not FactA( id == 4 )
    output.add("there's no FactA id 4");

- This rule is fired and the message is added to my output object.

Later on, I have a notification that a FactA has changed, then I:
- retract all FactAs from my working memory
- clear all FactA-related messages from my output object
- reload FactAs (let's say now I have FactA(1), FactA(3), but NOT FactA(4))
- reinsert them in the WM
- fire the rules

The rule that checks that there's no FactA(4) doesn't refire.

Why should it? The truth of the non-existance of FactA(4) has been established, and this truth never changed, certainly not by removing any FactA(n) and also not by inserting any FactA(x) with x!= 4.

As a solution, you could
- establish an explicit fact, asserted in rule "test non existence" and retracted by a rule checking the negated condition;
- add a Trigger fact to rule "test non existence" which you modify after each reload of the FactA set
- do something else which I'm not clever enough to think about at the moment