Nonmonotonic inference operations

MICHAEL FREUND, DANIEL LEHMANN
1993 Logic Journal of the IGPL  
A. Tarski 21] proposed the study of in nitary consequence operations as the central topic of mathematical logic. He considered monotonicity to be a property of all such operations. In this paper, we weaken the monotonicity requirement and consider more general operations, inference operations. These operations describe the nonmonotonic logics both humans and machines seem to be using when infering defeasible information from incomplete knowledge. We single out a number of interesting families
more » ... inference operations. This study of in nitary inference operations is inspired by the results of 11] on nitary nonmonotonic operations, but this paper is self-contained. 1. is asymmetric i 8s; t 2 U such that s t, we have t 6 s,
doi:10.1093/jigpal/1.1.23 fatcat:5fqmsuxcorahress7mj5b7hup4