Re: Boolean Value Warnings in Java

I actually wasn't able to reproduce the warning, but that's somewhat besides
the point, and I only tried with the Lisp version of s-ask.  There are a couple
of comments:

(1) PowerLoom does't really fully support boolean-valued functions, since they
are not strictly necessary.  Instead of a boolean-valued function, you can
always define a relation with one less argument whose truth value will
correspond to the boolean value.  For example:

(defrelation unhappy ((?c city)))

(2) You can define a boolean-valued function the way you had it, but you won't
get all the inferences you expect.  For example, if you ask

(ask (not (= (unhappy newyork)TRUE)))
=> FALSE

(ask (= (unhappy newyork) false))
=> FALSE

you get correct answers because of PowerLoom's reasoning about the
single-valuedness of the function, not because of its boolean value type.

However, if you assert

(assert (not (= (unhappy la) true)))

and then ask

(ask (= (unhappy la) false))
=> UNKNOWN

which is not what you'd expect.

(3) If you don't mind these issues but want to stay with boolean values, you
could just define the function without the boolean value type, and the warning
should go away - even though I'm not fully sure why you are getting it at all:

(deffunction unhappy ((?c city)) :-> ?b)

We might provide more general support for boolean-valued functions sometime in
the future given that that is a modeling style used in Semantic Web languages
that do not support unary relations.

Hans

>>>>> lee martie <[email protected]> writes:

>  From the powerloom 4.0.0.beta command line in the module PL-USER I can:
> (defconcept city)
> (assert (city newyork))
> (deffunction unhappy ((?c city)) :-> (?b BOOLEAN))
> (assert (=(unhappy newyork)TRUE))
> (ask(=(unhappy newyork)TRUE))

> and get an answer of TRUE.

> Attempting the same example above using the powerloom.jar that comes
> with powerloom 4.0.0.beta gives me a warning.
> If I ask "(=(unhappy newyork)TRUE)" with the method
> PLI.sAsk in the module PL-USER I get the warning:

> WARNING: Type check violation on argument `@TRUE' in proposition
>     (= (UNHAPPY NEWYORK) TRUE).
>     Argument must have type `BOOLEAN'.
>     Warning occurred while parsing the proposition:
>     (KAPPA () (UNHAPPY @NEWYORK @TRUE))

> and an answer of TRUE.

> Am I using the wrong values for booleans?
> Is there any advice on how to get rid of these warnings?

> Thanks for your help.
> Lee Martie


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