Ex contradictione nihil sequitur

In the logical semantics of knowledge bases (K8) the handling of contradictions poses a problem not solvable by standard logic. An adequate logic for KBs must be capable of tolerating inconsistency in a KB without los­ ing its deductive content. This is also the bottom line of so-called paraconsistent logics. But paraconsistent logic does not address the question whether contradictory information should be accepted or not in the derivation of further information depending on it . We propose two computational logics based on the notions of support and acceptance han­ dling contradictions in a conservative, resp. skeptical, manner: they neither lead to the break-down of the system nor are they ac­ cepted as valid pieces of information,