The P-Systems: A Systematic Classification of Logics of Nonmonotonicity

In the last years many logics of nonmonotonicity have been developed using various different formalisms and axiomatizations which makes them very difficult to compare. We develop a classification scheme for these logics using only a few simple concepts and axioms based on conditional logics, properties of partial preorders of possible states (worlds) and centering assumptions. Our framework (the P-Systems) allows us to discuss the similarities, main differences and possible extensions of these logics in a simple and natural way.