TITLE: ``Logic Programs with Multiple Forms of Default Negation''

ABSTRACT:

In everyday reasoning, we are accustomed to infer negated information from positive information. From a statement like ``the museum opens from Tuesday to Sunday'' we immediately conclude that the museum is not open on Mondays. Logic programming and non-monotonic reasoning have developed several theories for interpreting negated information and for deducing it from positive data. These notions of negation have been used as separate ways to interpret and to deduce negated information. That is, each application has chosen one of these notions of negation and has applied it to every piece of data in the domain of the application. However, in everyday reasoning we know that it is not natural to uniformly use a single rule for negation. Therefore, expressive power is undoubtedly gained by allowing the interaction of different theories for negation in the same application.

In this talk, a new class of logic programs containing two forms of default negation in addition to explicit (or ``classical'') negation is introduced. The semantics of these programs is defined and its properties are investigated.

Everyone is welcome to attend.