Obtenção de respostas baseadas em casos a partir de árvores de prova

Abstract

This dissertation investigates the set of answers to existentially quantified questions in the context of a system that represents its deductions by proof trees. In particular, in those situations in which a disjunctive answer is obtained, this dissertation proposes that a case-based answer should be provided instead. First, it is presented a formal definition of answers in the context of a proof tree based system, which considers that even proof trees generated at the intermediate steps of a deduction may produce possible answers to the question. The set of answers in accordance with the given definition is then partitioned into three answer classes, termed extensional, intensional and hypothetical answers, and it is showed that any of these three answer types may correspond to a disjunctive answer. To those situations where the system produces a disjunctive answer that has the general form P(A1) V P(A2) V ... V P(Ak), it is proposed an algorithm that from the answer deducti on in the form of a proof tree, is capable to determine a case-based answer to the exact same question. A case-based answer is an answer defined in terms of a finite and exhaustive number of cases in the problem domain, where each case implies in a non disjunctive answer P(Ai) to the question.