if a fact justifies itself, its probably best to just do nothing?
Juergen wrote:
My point of view is not so much if it makes sense to have such a rule,
but more that A => A is a legal rule and drools should deal with it
correctly.
Other interesting cases are:
not A => A, with and without no-loop attribute set to true
As asked, I added a JIRA, including 4 test cases:
http://jira.jboss.com/jira/browse/JBRULES-233
Juergen
Mark Proctor wrote:
Should a fact be allowed to justify itself? I'm not sure that make
sense.
Mark
Juergen wrote:
A logically asserted object seems to be retracted only when the
fact(s) leading to its inital assertion are invalid/retracted. Even
if the depended object is "backed" by some other rule/facts.
so in the following example:
1 => A
2 => A
As soon, as 1 is asserted, A is asserted. When 2 is asserted, the
truth of A is "backed" but nothing happens as A is already asserted
(in terms of memory management, the reference counter would increase
i guess).
When 1 becomes false and is retracted, the truth of A is still given
by 2 => A and A should not be retracted (which it is). Only if 2
also becomes false and is retracted, A should be retracted too.
Gets even more interesting if a fact is backed by itself after
inital assertion: A => A
Without this behaviour logical assertion are not useful in my opinion.
Checked it with JESS which does it properly.
Will it change in the future, and probably already for 3.0?
Juergen.
Example:
--------
DRL:
----
rule "1"
when
s : String()
then
System.out.println("s=" + s);
end
rule "2"
when
i : Integer()
then
System.out.println("i=" + i);
assertLogical("A");
end
Java:
-----
FactHandle h = workingMemory.assertObject(new Integer(1));
workingMemory.fireAllRules();
workingMemory.assertObject(new Integer(2));
workingMemory.fireAllRules();
workingMemory.retractObject(h); // A will be retracted, but should not
workingMemory.fireAllRules();
List l = workingMemory.getObjects();
System.out.println(l);
