[rules-users] Nested negation constraints behavior change from Drools 5.x to 6.x

[mikerod]

With both Drools v5.5.0.Final and v5.6.0.Final I observe a different behavior
than in both v6.0.0.Final and v6.0.1.Final.
in certain rules with negation wrapped around nested constraints.

I have tried to make the simplest rules to demonstrate the situation.

With a kb consisting of the following rules, which I have comments on that
describe what I've
found with the situation:

```
// Enabling this rule, makes "negation_over_nested" and
// "negation_distributed_partially_sharing" fire;
// without it they do not.
// 
// I think this is due to some shared structure
//  in the underlying subnetwork (I believe this is referred to as a
"segment").
// Perhaps it makes them "linked" in when otherwise they are being missed.

/**  *This is commented out, uncommenting causes different firing of other
rules*
rule shared_conjunct
when
	(not (String() and Integer()))
then
	System.out.println("shared_conjunct");
end
*/

// Won't fire with no wm facts UNLESS 
// it shares (I think) a node/subnetwork/segment with constraints 
// in a rule like "rule shared_conjunct" that DOES fire
rule negation_over_nested
when
  not ( (String() and Integer())
   		or 
   		(String() and Integer()))
then 
	System.out.println("negation_over_nested");
end

// Won't fire with no wm facts
rule negation_distributed_partially_no_sharing
when
	(not (String() and Long()))
	and 
	(not (String() and Long()))	
then 
	System.out.println("negation_distributed_partially_no_sharing");
end

// Same situation as "negation_over_nested"
rule negation_distributed_partially_sharing
when
	(not (String() and Integer()))
	and 
	(not (String() and Integer()))	
then 
	System.out.println("negation_distributed_partially_sharing");
end

// DOES fire with no wm inserts.
// DOES NOT need "shared_conjunct" to work
rule negation_distributed_fully
when
	((not String()) or (not Integer()))
	and
  	((not String()) or (not Integer()))
then 
	System.out.println("negation_distributed_fully");
end

```

--- 

This is the only 2 rules in the kb.  Running a session, with no facts
inserted and then firing all rules.

---
Drools v5.x output 

with "shared_conjuct" rule uncommented:
```
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_partially_no_sharing
negation_distributed_partially_sharing
negation_over_nested
shared_conjunct
fired: 8
time elapsed: 0.0
done
```

with "shared_conjuct" rule commented out:
```
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_partially_no_sharing
negation_distributed_partially_sharing
negation_over_nested
fired: 7
time elapsed: 0.0010
done
```

---
Drools v6.x output:
with "shared_conjuct" rule uncommented:
```
shared_conjunct
negation_over_nested
negation_distributed_partially_sharing
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
fired: 7
time elapsed: 0.0
done
```

with "shared_conjuct" rule commented out:
```
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
negation_distributed_fully
fired: 4
time elapsed: 0.0
done
```

I do note in the v6.x output, "negation_distributed_partially_no_sharing"
never fires, since it is specifically not sharing any
negated conjunt with the other rules.  This seems to correlate with whether
or not these rules fire.
Also, I realize my terminology is slightly off.  I think this is an issue
with rules having shared "segments", where 
one of these segments that is shared is the negation subnetwork introduced
in "shared_conjunct".

I also note that "negation_distributed_fully" always fires, independent of
any potential "segment" sharing.

As I mentioned in a comment on "shared_conjuct", I'm thinking this relates
to the newer PHREAK algorithm vs the original ReteOO.

Is this expected?  Is there something incorrect about the structure of the
negation rules?
Perhaps I have stumbled upon a defect?

I have not had time to do any sort of deeper debugging into the issue, if I
find out more info, I'll post it up here.

p.s. I know the types are not meaningful, this is just an example to show
the difference.  I hope it accomplishes this goal.




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