[PowerLoom Forum] play(player, game)

[Thomas Russ]

I'll let Hans handle the other issues, but I'll tackle closed world.

On May 24, 2005, at 10:38 PM, Octav Popescu wrote:

> Then I guess my question is again: Any idea when you'll issue the next 
> release? :-)
>
> Related to the problem with the CLOSED relations, I was trying to 
> think of possible problems, so I was wondering if you would fix that 
> only at the top level, or also at intermediate levels in the reasoning 
> process. Like for instance if one tries to prove (AND (P1 A) (P2 A)), 
> and (P1 A) is TRUE and (P2 A) cannot be proved but is declared CLOSED, 
> would the whole result be FALSE?

That would be my preferred solution.  That is, in part, why
it is taking a while to get something running out.

>  Can this be generalized to quantified formulas?

I think so.  It really depends on how sophisticated our code
is for determining which propositions are closed, so I can't
really guarantee it.

> Another question: irrespective of the CLOSED declaration, does 
> PowerLoom do 3-value (or 5-value with the defaults) logic computation? 
> Like saying (AND UNKNOWN FALSE) = FALSE, (AND UNKNOWN TRUE) = UNKNOWN, 
> (OR UNKNOWN TRUE) = TRUE, (OR UNKNOWN FALSE) = UNKNOWN.
>
> Thanks,
> Octav
>
> --On Tuesday, May 24, 2005 6:46 PM -0700 Hans Chalupsky <hans at ISI.EDU> 
> wrote:
>
>> Octav,
>>
>> you are right that the primary reason for this is the asymmetric
>> effort by PowerLoom on proving the query as stated as opposed to
>> trying to prove its negation.  You are also right that the system
>> looks somewhat stupid/buggy using this behavior when querying closed
>> relations.  Tom Russ was offended by this also recently and has been
>> working on a fix.  I'm not sure exactly where we are on this, but
>> we'll try to fix this for the next release.
>>
>> Hans
>>
>>>>>>> Octav Popescu <octav at cmu.edu> writes:
>>
>>> Hans,
>>> After looking a little into this, now I'm confused too about the 
>>> semantics
>>> of  the CLOSED predicate. :-) I understand why the example below 
>>> does not
>>> lead to  any contradictions. But I'm not sure I understand why 
>>> CLOSED only
>>> has effect  on NOT questions. Like for instance:
>>
>>> ? (defconcept player)
>>> | c|PLAYER
>>> ? (assert (closed player))
>>> | P|(CLOSED PLAYER)
>>> ? (assert (player jano))
>>> | P|(PLAYER JANO)
>>> ? (ask (not (player chess)))
>>> Processing check-types agenda...
>>> TRUE
>>> ? (ask (player chess))
>>> UNKNOWN
>>
>>> I'm not sure I understand why the last query doesn't return FALSE. I 
>>> take
>>> it  it has to do with the fact that PowerLoom doesn't put much 
>>> effort into
>>> disproving a query. The manual says:
>>
>>> "The PowerLoom command ask returns one of three values: true if it 
>>> can
>>> prove  the truth of a proposition, false if it can easily prove the
>>> falsity of a  proposition and otherwise it returns unknown."
>>
>>> So in this case PowerLoom does know that the query failed, and it 
>>> seems to
>>> me  it would be easy to check that the predicate is CLOSED, and then
>>> change the  result to FALSE. This would be more in line with the 
>>> "negation
>>> as failure"  mode. Is there a problem with this?
>>
>>> Thanks,
>>> Octav
>>
>>> --On Friday, May 13, 2005 13:11 -0700 Hans Chalupsky <hans at ISI.EDU> 
>>> wrote:
>>
>>>> Krzysztof,
>>>>
>>>> I'm not sure why you think the last assertion should not be 
>>>> possible.
>>>> At that point both JANO and CHESS are of type PLAYER (via explicit
>>>> assertion) and GAME (inferred via the type constraint on PLAY).  You
>>>> asserted GAME and PLAYER to be closed which only means (NOT 
>>>> (GAME/PLAYER
>>>> ?x))  will be concluded if (GAME/PLAYER ?x) cannot be inferred.  
>>>> So, there
>>>> are no contradictions I can see.
>>>>
>>>> Hans
>>>>
>>>>>>>>> Krzysztof Janowicz <k at janowicz.de> writes:
>>>>
>>>>> hi,
>>>>> i do not understand why the last assert is possible, can anyone 
>>>>> give me
>>>>> a hand? can i assert everything independent of the definitions made
>>>>> bevor?
>>>>
>>>>> thanks!
>>>>
>>>>> (DEFCONCEPT PLAYER)
>>>>> (DEFCONCEPT GAME)
>>>>> (DEFRELATION PLAY (?X ?Y)
>>>>> :=> (AND (PLAYER ?X) (GAME ?Y)))
>>>>
>>>>> // or (defrelation play ((?x player) (?y game)))
>>>>
>>>>> (ASSERT (CLOSED GAME))
>>>>> (ASSERT (CLOSED PLAYER))
>>>>> (ASSERT (PLAYER JANO))
>>>>> (ASSERT (PLAYER CHESS))
>>>>> (ASSERT (PLAY JANO CHESS))
>>>>> (ASSERT (PLAY JANO JANO))
>>>>
>>>>
>>>>> regards
>>>>> k.janowicz
>>>>> _______________________________________________
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>>>>> powerloom-forum at isi.edu
>>>>> http://mailman.isi.edu/mailman/listinfo/powerloom-forum
>>>>
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>>
>>
>
>
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