Reasoning by Cases without Contraposition in Default Logic

Default logic, one of the best known formalisms to express common sense reasoning, does not allow to reason by cases in its standard formulations. We propose a natural and easy way of translating rules with exceptions into standard defaults, which allows to reason by cases without giving any unwanted contraposition. This solution is the simplest possible extension to the first coming idea consisting in taking the defaults by sets. Thus we keep the attractive simplicity of default logic basically intact. Our solution is independant of the notion of "commitment" and can as well be applied to the versions of default logic caring about commitment. We provide several examples in order to make precise what is wanted. We study various other proposals in the literature, showing that either they give some kind of unwanted contraposition or that they need a new and non standard form of disjunction and that they greatly modify the notion of default reasoning.

• Type: Conference
• Year: 1994
• Where: ECAI
• Authors: Yves Moinard
• Keywords: Artificial Intelligence, Common Sense Reasoning, Default Logic, ECAI 1994, Unwanted Contraposition