[rules-users] Negation semantics in Drools
Greg Barton
greg_barton at yahoo.com
Sat Apr 18 02:27:38 EDT 2009
I managed to get drools to work the same way no matter what the insertion order. (See attached eclipse project.)
Basically I created a custom conflict resolver that preempts the use of recency: it orders matched tuples according to their objects' hash codes first. (That technically won't work to completely ignore recency in all cases because of the way most java VMs create default hash codes, but it's good enough for this example.) It's possible that Jess uses a conflict resolution rule like this by default and that's why it has this result out of the box.
--- On Fri, 4/17/09, Paul Fodor <paul.i.fodor at gmail.com> wrote:
> From: Paul Fodor <paul.i.fodor at gmail.com>
> Subject: Re: [rules-users] Negation semantics in Drools
> To: "Rules Users List" <rules-users at lists.jboss.org>
> Date: Friday, April 17, 2009, 11:28 PM
> Hi Edson,
>
> 2009/4/17 Edson Tirelli <tirelli at post.com>
>
> >
> >
> > Paul,
> >
> > I am not an expert on logic programming, but in
> this case, your example
> > is negating a goal (not a fact) in the backward
> chaining:
> >
> > win(X):- move(X,Y), not(win(Y)).
> >
> > Pure forward chaining systems don't have goals,
> since they are data
> > driven.
> >
> > I don't think this would be a good or fair
> comparison because it is
> > comparing a native concept in one side and an emulated
> concept in the other
> > side. If you were negating an actual fact, the
> comparison would be more an
> > apples-to-apples comparison.
>
>
> >From the logic point of view, win/2 and move/2 are both
> literals (atoms, if
> no explicit negation is used) and we define clauses (which
> can be
> facts or rules). The logical semantics (well-founded model
> theory or stable
> model semantics) makes no distinction between the negation
> of a literal
> move/2 (defined through a set of facts) and the negation of
> a literal win/2
> (which is defined through a recursive rule).
>
> These are declarative semantics and have nothing to do with
> the operational
> semantics (how to actually compute them).
> There are forward chaining systems (such as: DLV,
> OntoBroker from Ontoprise,
> IRIS) that compute them as well as some top-down systems
> (tabled XSB, Yap).
>
> We are interested in measuring the performance for a set of
> features
> that are considered important for the Semantic Web
> (computing logical
> models, dynamic updates, joins or relations, recursion
> rules, persistent
> data, etc.). For all these features we wanted to test the
> technology for
> rule systems (production rule systems were one of the
> technologies we
> studied). I agree that production rule systems are more fit
> for other
> tasks (for instance, reactive rules), but we wanted to see
> if they can be
> easily used for the Semantic Web tasks. For each feature
> that we tested, we
> tried our best to represent it in the best way for every
> given system. We
> are always open to sugestions of other banchmarks to test.
>
> Regards,
> Paul
>
>
> >
> > Just my .02c
> >
> >
> > Edson
> >
> > 2009/4/17 Paul Fodor <paul.i.fodor at gmail.com>
> >
> >> Now, I am curious. What is the background on
> this exercise? There are
> >>> some problems that are better suited for
> backward and others better suited
> >>> for forward chaining. Most problems would be
> modeled in very different ways
> >>> in each technology.
> >>
> >>
> >> It is just a set of tests we made in a suite of
> benchmarks. We wanted
> >> compare and benchmark both the different the
> technologies and various rule
> >> systems.
> >>
> >>
> >>> If we were just searching for the solution,
> it would just be the case
> >>> of writing (in forward chaining) one or two
> rules that would provide the
> >>> correct answer. But since this seems to be an
> academic exercise, I am
> >>> curious to understand the goals of it so that
> we can properly model it.
> >>
> >>
> >> The goal of this particular test (and our other
> stratified or
> >> non-stratified tests) was to see how efficient are
> implementations of
> >> default negation in rule systems. Programs using
> negation can be very
> >> various, but we tried to come up with a bunch of
> standard classic problems
> >> and implemented them in the best way possible in
> each rule system.
> >>
> >> You are right that each technology has its own
> strong and weak points
> >> depending on the tasks intended to solve. Even the
> way of implementing each
> >> particular task differs a lot on various rule
> systems.
> >>
> >> Regards,
> >> Paul.
> >>
> >>
> >>> Cheers,
> >>
> >>
> >>> Edson
> >>>
> >>> 2009/4/17 Paul Fodor
> <paul.i.fodor at gmail.com>
> >>>
> >>>> Hi Edson,
> >>>>
> >>>> The "insertLogical" doesn't
> work for non-stratified programs.
> >>>> For instance, in the win-nowin example, if
> there is a move(1,2) and
> >>>> a move(2,1), the order in which the two
> facts are inserted determines the
> >>>> final model (please see hte tests below).
> >>>>
> >>>> In logic programming, this example has two
> stable models: {win(1)} and
> >>>> {win(2)}, or a well-founded model {}
> (win(1) and win(2) are both undefined).
> >>>>
> >>>> Regards,
> >>>> Paul.
> >>>> *
> >>>>
> >>>> package
> >>>> *tests;
> >>>>
> >>>> *
> >>>>
> >>>> import
> >>>> *tests.Test.Win;*
> >>>>
> >>>> import
> >>>> *tests.Test.Move;
> >>>>
> >>>> *
> >>>>
> >>>> rule
> >>>> *"direct"
> >>>>
> >>>> *when*
> >>>>
> >>>> m : Move(x : first, y : second)
> >>>>
> >>>> *not* Win(first == y)
> >>>>
> >>>> *then*
> >>>>
> >>>> *insertLogical*(*new* Win(m.getFirst()));*
> >>>>
> >>>> end
> >>>> *
> >>>>
> >>>> move
> >>>>
> >>>> 1
> >>>>
> >>>> 2
> >>>>
> >>>> move
> >>>>
> >>>> 2
> >>>>
> >>>> 1
> >>>>
> >>>> Test:
> >>>>
> >>>> reading rulefile: win.drl ...
> >>>>
> >>>> reading datafile: win_upper3_drools.drools
> ...
> >>>>
> >>>> loading cputime: 0.016
> >>>>
> >>>> loading walltime: 0.016
> >>>>
> >>>> calculating ...
> >>>>
> >>>> computing cputime: 0.0
> >>>>
> >>>> computing walltime: 0.0040
> >>>>
> >>>> Derived facts in memory:move(1, 2).
> >>>>
> >>>> win(2).
> >>>>
> >>>> move(2, 1).
> >>>>
> >>>> 3
> >>>>
> >>>> move
> >>>>
> >>>> 2
> >>>>
> >>>> 1
> >>>>
> >>>> move
> >>>>
> >>>> 1
> >>>>
> >>>> 2
> >>>>
> >>>> Test:
> >>>>
> >>>> reading rulefile: win.drl ...
> >>>>
> >>>> reading datafile: win_upper4_drools.drools
> ...
> >>>>
> >>>> loading cputime: 0.016
> >>>>
> >>>> loading walltime: 0.016
> >>>>
> >>>> calculating ...
> >>>>
> >>>> computing cputime: 0.0
> >>>>
> >>>> computing walltime: 0.0040
> >>>>
> >>>> Derived facts in memory:move(2, 1).
> >>>>
> >>>> win(1).
> >>>>
> >>>> move(1, 2).
> >>>>
> >>>> 3
> >>>>
> >>>> 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
> >>>> >>>>
> >>>> >>>>
> >>>> >>>>
> >>>> >>>>
> _______________________________________________
> >>>> >>>> rules-users mailing list
> >>>> >>>>
> rules-users at lists.jboss.org
> >>>> >>>>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>>> >>>>
> >>>> >>>
> >>>> >>>
> >>>> >>>
> >>>> >>> --
> >>>> >>> 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
> >>>> >>>
> >>>> >>
> >>>> >>
> >>>> >>
> _______________________________________________
> >>>> >> rules-users mailing list
> >>>> >> rules-users at lists.jboss.org
> >>>> >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>>> >>
> >>>> >
> >>>> >
> >>>> >
> >>>> > --
> >>>> > 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
> >>>> >
> >>>>
> >>>>
> >>>>
> >>>>
> _______________________________________________
> >>>> rules-users mailing list
> >>>> rules-users at lists.jboss.org
> >>>>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>>>
> >>>>
> >>>
> >>>
> >>> --
> >>> 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
> >>>
> >>>
> >>
> >> _______________________________________________
> >> rules-users mailing list
> >> rules-users at lists.jboss.org
> >>
> https://lists.jboss.org/mailman/listinfo/rules-users
> >>
> >>
> >
> >
> > --
> > 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
> >
> >
> _______________________________________________
> rules-users mailing list
> rules-users at lists.jboss.org
> https://lists.jboss.org/mailman/listinfo/rules-users
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