[PowerLoom Forum] Question about closed world

[Anderson]

Hello

I can't understand the CLOSED world in PowerLoom. I think the correct 
answer of the last question (text below) is FALSE, but a receive an 
UNKNOWN. Please, can someone help-me? Thanks in advance.

Anderson from São Paulo, Brasil.
MSN: f1r3574r73r at hotmail.com
ICQ: 124462208


(defconcept ACONCEPT)
(defconcept BCONCEPT)
(assert (ACONCEPT A))
(ask (not (BCONCEPT A)))
    UNKNOWN
(ask (BCONCEPT A))
    UNKNOWN
(assert (CLOSED BCONCEPT))
(ask (not (BCONCEPT A)))
    TRUE
(ask (BCONCEPT A))
    UNKNOWN