[rules-users] Negation semantics in Drools
Paul Fodor
paul.i.fodor at gmail.com
Fri Apr 17 16:19:30 EDT 2009
I see. Thank you,
Paul.
2009/4/17 Edson Tirelli <tirelli at post.com>
>
> I did not had time to analyze what jess is doing, but note that what is
> important is the final answer. In your example, with Move(1,2) and
> Move(2,3), the final answer must be Win(2), right? And that is what Drools
> will answer, does not matter the order in which the data is entered into the
> engine.
>
> BUT, *very important*: the following construct in backward chaining:
>
> win(X):- move(X,Y), not(win(Y)).
>
> Is better represented in forward chaining using *logicalInsert* instead
> of a regular *insert*:
>
> rule "direct" % Drools
> when
> m : Move(x : first, y : second)
> not Win(first == y)
> then
> logicalInsert(new Win(m.getFirst()));
> end
>
> Since in your backward chaining rule, only one win() predicate
> instantiation will remain true.
>
> So, even with differences in the reasoning algorithm, the answer is
> correct.
>
> Please explain further if I am missing anything.
>
> Edson
>
>
> 2009/4/17 Paul Fodor <paul.i.fodor at gmail.com>
>
> 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
>>>
>>> _______________________________________________
>>> 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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> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
>
>
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