The revision of beliefs is an important general purpose functionality that an agent must exhibit. The agent usually needs to perform this task in cooperation with other agents, because access to knowledge and the knowledge itself are distributed in nature. In this work, we propose a new approach for performing belief revision in a society of logic-based agents, by means of a (distributed) genetic algorithm, where the revisable assumptions of each agent are coded into chromosomes as bit-strings. Each agent by itself locally performs a genetic search in the space of possible revisions of its knowledge, and exchanges genetic information by crossing its revisable chromosomes with those of other agents. We have performed experiments comparing the evolution in beliefs of a single agent informed of the whole of knowledge, to that of a society of agents, each agent accessing only part of the knowledge. In spite that the distribution of knowledge increases the difficulty of the problem, experimental results show that the solutions found in the multi-agent case are comparable in terms of accuracy to those obtained in the single agent case. The genetic algorithm we propose, besides encompassing the Darwinian operators of selection, mutation and crossover, also comprises a Lamarckian operator that mutates the genes in a chromosome as a consequence of the chromosome phenotype's individual experience obtained while solving a belief revision problem. These chromosomic mutations are directed by a logic-based belief revision procedure that relies on tracing the logical derivations leading to inconsistency of belief, so as to remove these derivations' support on the gene coded assumptions, effectively by mutating the latter. Because of the use a Lamarckian operator, and following the literature, the genes in these chromosomes that are modified by the Lamarckian operator are best dubbed ``memes'', since they code the memory of the experiences of an individual along its lifetime, besides being transmitted to its progeny. We believe our method to be important for situations where classical belief revision methods hardly apply: those where environments are non-uniform and time changing. These can be explored by distributed agents that evolve genetically to accomplish cooperative belief revision, if they use our approach.
Belief revision by multi-agent genetic search
LAMMA, Evelina;RIGUZZI, Fabrizio;
2001
Abstract
The revision of beliefs is an important general purpose functionality that an agent must exhibit. The agent usually needs to perform this task in cooperation with other agents, because access to knowledge and the knowledge itself are distributed in nature. In this work, we propose a new approach for performing belief revision in a society of logic-based agents, by means of a (distributed) genetic algorithm, where the revisable assumptions of each agent are coded into chromosomes as bit-strings. Each agent by itself locally performs a genetic search in the space of possible revisions of its knowledge, and exchanges genetic information by crossing its revisable chromosomes with those of other agents. We have performed experiments comparing the evolution in beliefs of a single agent informed of the whole of knowledge, to that of a society of agents, each agent accessing only part of the knowledge. In spite that the distribution of knowledge increases the difficulty of the problem, experimental results show that the solutions found in the multi-agent case are comparable in terms of accuracy to those obtained in the single agent case. The genetic algorithm we propose, besides encompassing the Darwinian operators of selection, mutation and crossover, also comprises a Lamarckian operator that mutates the genes in a chromosome as a consequence of the chromosome phenotype's individual experience obtained while solving a belief revision problem. These chromosomic mutations are directed by a logic-based belief revision procedure that relies on tracing the logical derivations leading to inconsistency of belief, so as to remove these derivations' support on the gene coded assumptions, effectively by mutating the latter. Because of the use a Lamarckian operator, and following the literature, the genes in these chromosomes that are modified by the Lamarckian operator are best dubbed ``memes'', since they code the memory of the experiences of an individual along its lifetime, besides being transmitted to its progeny. We believe our method to be important for situations where classical belief revision methods hardly apply: those where environments are non-uniform and time changing. These can be explored by distributed agents that evolve genetically to accomplish cooperative belief revision, if they use our approach.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
