[PowerLoom Forum] play(player, game)

[Octav Popescu]

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? Can this be generalized to quantified formulas?

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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>
>