2 research outputs found
Modelling rational inquiry in non-ideal agents
No full textde la tesi doctoralL'objectiu principal del treball realitzat ha sigut el desenvolupar una manera de modelar el proc茅s d'investigaci贸 racional (l'evoluci贸 de les creences d'un agent racional com a conseq眉猫ncia de la seva interacci贸 amb l'entorn i dels seus procesos d'infer猫ncia), mantenint la idea general del model dels m贸ns possibles i la sem脿ntica de Kripke, per貌 intentant evitar els problemes de l'omnisci猫ncia l貌gica i el raonament ideal. Les contribucions principals del treball s贸n:路 S'ha fet un estudi molt detallat sobre les diferents propostes que s'han fet en el tema del tractament formal del problema de l'omnisci猫ncia l貌gica en les l貌giques modals de creences. Aquest estudi ressalta les semblances i difer猫ncies entre les diverses solucions i mostra fins a quin punt solucionen el problema del raonament ideal.路 Com a resultat d'aquest estudi, es suggereix una nova aproximaci贸 al problema, basada en el concepte dels m贸ns impossibles. La idea principal 茅s que una situaci贸 pot ser percebuda de diferents maneres per diferents agents; aix铆, una situaci贸 pot ser descrita de forma subjectiva per cadascun d'ells. A m茅s, en cada situaci贸 un agent pot tenir raons per recolzar i/o rebutjar determinats fets. La percepci贸 que un agent t茅 del seu entorn determina les seves creences en aquella situaci贸. Aquestes s贸n les idees b脿siques del concepte de situacions subjectives proposat a la tesi.路 S'ha determinat quines s贸n les activitats b脿siques que poden modificar les creences d'un agent racional (realitzaci贸 de deduccions, plantejament de dubtes, plantejament de preguntes a l'entorn i rebuda de dades externes). Tamb茅 s'ha definit una classe espec铆fica d'agents racionals, els investigadors racionals, que realitzen aquestes activitats d'una forma concreta (manipulant f贸rmules de primer ordre en un arbre de taulers anal铆tics).路 Per 煤ltim, a la tesi es mostra com l'evoluci贸 de les creences dels investigadors racionals, causada per la seva an脿lisi din脿mica multi-dimensional, pot ser modelitzada formalment dins del marc de les situacions subjectives. Aix貌 es fa utilitzant les situacions concebibles, que corresponen a aquells escenaris que l'agent pot considerar, independenment de la seva possible parcialitat o inconsist猫ncia. L'evoluci贸 de les creences d'un agent es modelitza amb la generaci贸 d'una seq眉猫ncia de relacions d'accessibilitat, en la que, despr茅s de cada pas d'an脿lisi de les creences, van canviant les situacions concebibles considerades com a alternatives viables per l'agent.of the PhD thesisThe main aim of this work has been to develop a way to model the process of rational inquiry (the evolution of a rational agent's set of beliefs over time as a consequence of its interaction with the world and its internal inferential processes), keeping the general idea of the possible worlds model and the Kripke semantics but trying to avoid the problems of logical omniscience and perfect reasoning. The actual contributions of the work described in the thesis are the following:路 An extensive survey of the state of the art has been made, in which the most relevant approaches that have been proposed to solve the problems of logical omniscience and perfect reasoning are presented. This review focuses on the similarities and differences between the various solutions and shows to which degree they provide a framework in which it is possible to model non-ideal reasoners.路 As a result of this study, an impossible-worlds based framework in which logical omniscience is avoided is suggested. The main idea of this proposal is that a situation may be perceived in different ways by different agents; thus, a situation may be described subjectively by each of them. Furthermore, in each situation an agent may have reasons to suport and/or reject certain facts. The perception that an agent has of a situation will determine its beliefs in that situation. These are the basic ideas underlying the subjective situations described in the dissertation.路 It has been determined which are the basic activities that may modify the set of beliefs of a rational agents (performing deductions, posing doubts, making questions to the environment and receiving external data). A specific class of rational agents, called rational inquirers, is also defined. These agents perform their doxastic activities in a concrete way, which is based in the manipulation of first-order formulae contained in an analytic tableaux tree. 路 Finally, in the dissertation it is shown how the evolution of the beliefs of the rational inquirers, caused by their dynamic multi-dimensional analysis, may be formally modelled in the subjective situations framework. This modelling is performed using conceivable situations, which correspond to those scenarios that may be considered by the modelled agent, irrespective of their possible partiality or inconsistency. The evolution of the beliefs of an agent is modelled with the generation of a sequence of accessibility relations in which, after each step of belief analysis, the situations that are considered as viable by the agent change in an appropriate way
