Logic based Agents
� It’s possible to construct agent that reason based on knowledge expressed in terms of logic statements
� We are going to make a short review of Classic � We are going to make a short review of Classic Logic and then extend to Logic with the notions of belief and “local” knowledge and other modal operators (Modal Logic)
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Lógica Proposicional
� Algebra Booleana é uma sistematização da Lógica Proposicional como uma
álgebra
Forma Normal Conjuntiva
� A inferência por resolução é completa em FNC. Isto é pode derivar qualquer conclusão válida por qualquer base de conhecimento em Lógica Proposicional.
� Completo em um sentido especializado: Completeza da refutação. Pode
ser usado para confirmar se uma dada sentença é valida ou não, mas
não consegue enumerar todas as sentenças válidas
Lógica de Primeira Ordem
� Aqui percebemos que o mundo é repleto de objetos, alguns dos quais estão relacionados a outros objetos e tentamos raciocinar sobre eles
� Introduz-se as noções de : constantes, predicados, funções e variáveisfunções e variáveis
� Lógica de Primeira Ordem (LPO) também pode ser chamada de cálculo de predicados de primeira ordem (CPPO)
Another Example: The Muddy Children
� A group of n children enter the house after having
played in the mud outside. They are greeted in the
hallway by their father, who notices that k of the children have mud of their forecast. He makes the following
announcement, “At least one of you has mud on his forehead”. The children can all see each other’s forehead”. The children can all see each other’s foreheads, but not their own. The father than says “Do any of you know that you have mud on your forehead? If you do raise your hand now.” No one
raises his hand. The father repeats the question, and
again no one moves. The father does not give up and
keeps repeating the question. After exactly k rounds, all
the children with muddy foreheads raise their hands
simultaneously.4-42
Two children both muddy
� The solid boxes indicate the equivalences between possible words for agent 1
� The dashed boxes indicate the equivalences between possible words for agent 2
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Possible-Worlds approach discussion
� The ontology of possible worlds and accessibility relations…is frankly misterious to most practically minded people, and in particular has nothing to say about agent architecture [Seel, 1989 apud Wooldridge 2009]
� Despite the serious disadvantages, possible worlds are still the semantics of choice for many researchers in modal logic and several variations of basic possible-worlds have been proposed addressing the difficulties, see [Wooldridge and Jennings, 1995]
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