Semantics-based Nonmonotonic Inference

Semantics-based Nonmonotonic Inference

In this paper we discuss Gabbay’s idea of basing nonmonotonic deduction on semantic consequence in intuitionistic logic extended by a consistency operator and Turner’s suggestion of replacing the intuitionistic base system by Kleene’s three-valued logic. It is shown that a certain counterintuitive feature of these approaches can be avoided by using Nelson’s constructive logic N instead of intui...

Nonmonotonic Inference Based on Expectations

We show how nonmonotonic inferences may elegantly be interpreted in terms of underlying expectations. The fundamental idea is that when we reason, we make use of not only the information that we firmly believe, but also expectations that guide our beliefs without quite being part of them. We propose two ways of modelling the expectations used in nonmonotonic reasoning: by expectation sets, equi...

Preference-Based Semantics for Nonmonotonic Logics

A variant is proposed of the preference-based se­ mantics for nonmonotonic logics that was origi­ nally considered by Shoham [1987; 1988]. In this variant it is not assumed that preferences between standard models arc aggregated into one preference order. This allows the capturing of all main non­ monotonic formalisms, including Default Logic oi Reiter [1980]. The preferential models introduced...

Proteus: A Frame-Based Nonmonotonic Inference System

Semantics for Nonmonotonic Logics

A variant is proposed of the preference-based semantics for nonmonotonic logics that was originally considered by Shoham (1987,1988). In this variant it is not assumed that preferences between standard models are aggregated into one preference order. This allows the capturing of all main nonmonotonic formalisms, including Default Logic of Reiter (1980). The preferential models introduced in thi...