[rules-users] Negation semantics in Drools

[Paul Fodor]

Hi Edson, Greg,
I don't think the rule is written wrong. This is how the win-nowin program
is written in logic programming: X wins if there is a move from X to some Y
and Y doesn't win:
win(X):- move(X,Y), not(win(Y)).

rule "direct" % Drools
    when
        m : Move(x : first, y : second)
        not Win(first == y)
    then
 insert(new Win(m.getFirst()));
end

I think that it's interesting that, in Jess (another production rule
system), the stratified model is always computed right, no matter what was
the order of the facts in the database. If you want to take a look, please
see the equivalent program in Jess for win-nowin that I attached. Just run
it with:
jess test.clp

win_upper1_jess.jess

(move (cur 1) (next 2))
(move (cur 1) (next 3))
(move (cur 2) (next 4))
(move (cur 2) (next 5))
...

win_upper2_jess.jess

(move (cur 2) (next 4))
(move (cur 2) (next 5))
(move (cur 1) (next 2))
(move (cur 1) (next 3))
...

test.clp:

(deftemplate move (slot cur) (slot next))
(deftemplate win (slot val))

(defrule find_win
     (move (cur ?cur) (next ?next))
     (not (win (val ?next)))
     =>
     (assert (win (val ?cur)))
)

(defquery query-win
      (win (val ?val))
)
(open "win_result.txt" output a)
(printout output  ./win_upper1_jess.jess crlf)
(reset)
(load-facts "./win_upper1_jess.jess")
(bind ?tmx (call java.lang.management.ManagementFactory getThreadMXBean))
(deffunction cputime () (return (* (?tmx getCurrentThreadCpuTime) 1E-9)))
(bind ?starttime_wall (time))
(bind ?starttime_cpu (cputime))
(run)
(bind ?query_result (run-query* query-win))
(bind ?count 0)
(while (?query_result next)
    (++ ?count)
)
(printout output "solutions: " ?count crlf)
(bind ?endtime_cpu (cputime))
(bind ?endtime_wall (time))
(bind ?walltime (- ?endtime_wall ?starttime_wall))
(bind ?cputime (- ?endtime_cpu ?starttime_cpu))
(printout output "computing cputime: " ?cputime crlf)
(printout output "computing walltime: " ?walltime crlf)
(close output)

Regards,
Paul Fodor.
2009/4/16 Edson Tirelli <tirelli at post.com>

>
>    Ha, thanks a lot Greg. I need new glasses... he is actually comparing
> with the parameter "second", but when creating the win fact, using the
> parameter "first".
>
> not Win(first == m.second)
>   insert(new Win(m.first));
>
>    Yes, in this case the engine is working exactly as it should.
>
>    Anyway, I added the (fixed) test case to the codebase, just in case. :)
>
>    Thanks,
>        Edson
>
> 2009/4/16 Greg Barton <greg_barton at yahoo.com>
>
> You don't have to worry.  The engine is acting as it should.
>>
>> The rule Paul had was this, a bit simplified for clarity:
>>
>> rule "direct"
>> when
>>    m : Move()
>>    not Win(first == m.second)
>> then
>>        insert(new Win(m.first));
>> end
>>
>> If the insertion order is [Move(1,2), Move(2,3)] then the rule matches
>> first on Move(2,3) and Win(2) is inserted.  No other rule fires because now
>> Move(1,2) and Win(2) match up, removing the instantiation with Move(1,2)
>> from the agenda.
>>
>> If the insertion order is [Move(2,3), Move(1,2)] then the order is this:
>>
>> matched Move(1,2) insert Win(1)
>> matched Move(2,3) insert Win(2)
>>
>> The insertion of Win(1) in the first firing does NOT prevent the
>> instantiation with Move(2,3) from then firing.
>>
>> So it's all good. :)  Sample code and output attached.
>>
>> --- On Thu, 4/16/09, Greg Barton <greg_barton at yahoo.com> wrote:
>>
>> > From: Greg Barton <greg_barton at yahoo.com>
>> > Subject: Re: [rules-users] Negation semantics in Drools
>> > To: "Rules Users List" <rules-users at lists.jboss.org>
>> > Date: Thursday, April 16, 2009, 8:50 PM
>>  > It is on the latest snapshot release,
>> > 5.0.0.20090417.005612-483
>> >
>> > --- On Thu, 4/16/09, Edson Tirelli <tirelli at post.com>
>> > wrote:
>> >
>> > >     We need to investigate if that is still happening
>> > in
>> > > latest trunk.
>> >
>> >
>> >
>> > _______________________________________________
>> > rules-users mailing list
>> > rules-users at lists.jboss.org
>> > https://lists.jboss.org/mailman/listinfo/rules-users
>>
>>
>>
>>
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>>
>>
>
>
> --
>  Edson Tirelli
>  JBoss Drools Core Development
>  JBoss, a division of Red Hat @ www.jboss.com
>
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