A five-valued logic and a system

The present article introduces a five-valued logic and a deductive system. Here, the logic presented is a relevant fragment of the @-logic, which is also a space-time logic. These five values correspond to the following semantics: unknown, possibly known but consistent, false, true, and inconsistent. The present logic and the PLAIN programming language are two results of the same intuitions and from the same philosophical view. Finally, as well as the purposes of PLAIN, the logic ought to be used to support (mobile) agents systems in some manner, besides general purposes. Facultad de Informática