Uma lógica de descrição default

• Ano de defesa: 2011
• Autor(a) principal: Frota, Débora Farias
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: por
• Palavras-chave em Português: Ciência da computação; Lógica de descrição; Lógica default; Complexidade exptime; Description logic; Default logic; Exptime complexity; Lógica de primeira ordem; Lógica de computador; Algoritmos; Complexidade computacional
• Link de acesso: http://www.repositorio.ufc.br/handle/riufc/17798

Knowledge formalization and reasoning automatization are central within Arti cial Intelligence. First Order Logic has been traditionally used for such purposes. However, it is better suited to deal with complete knowledge in ideal circumstances. In real situations, in which the knowledge is partial, First Order Logic is not su cient. Nonmonotonic logics have been proposed to better cope with practical reasoning. A successful formalization of nonmonotonic reasoning is the Reiter's default logic which extends classical logic with default rules. Unfortunately, default logic is undecidable. In this work, we propose a description default logic expressible enough to formalize practical reasoning in knowledge bases. It has as its monotonic basis the ALC Description Logic. We add some restrictions to the application of defaults in order to obtain nice properties such as coherence and the elimination of anomalous extensions. We present the main algorithms used to build an extension with a step by step complexity analysis.