Model contractions on description logics

When using tableaux algorithms to reason about Description Logics (DLs), new information is inferred from the models considered while trying to achieve knowledge satisfiability. By focusing the ontology change problem, we consider an environment where DLs are the logical formalization to express knowledge bases in the web, and the integration of distributed ontologies is developed under new extensions of the belief revision theories originally exposed in [1]. Hence, a reinforced theory arises in order to properly apply change operations over models, considering new inferred information and assumed beliefs in each possible world. As a result, a new type of contraction operator is proposed and its success postulate analyzed.Red de Universidades con Carreras en Informática (RedUNCI

Consolidation of plausiblity relations in multi-agent systems

Within the context of multi-agent systems, an agent may often ¯nd itself in a position where it receives information through informants. These informants are independent agents who have their own interests and, therefore, are not necessarily completely reliable. It is natural for an agent to be more inclined to believe one informant over another, especially if the informant has proven itself reliable over a period of time. This preference is stored in a plausibility relation, a partial order indicating the relative credibility of the agent's informants. Through careless expansion or other means, inconsistencies may be introduced into the plausibility relation. A consolidation operator is proposed and characterized through a set of postulates. Alternative constructions are discussed. A non-prioritized revision operator for plausibility relations, based on consolidation, is also presented.Eje: Sistemas inteligentesRed de Universidades con Carreras en Informática (RedUNCI

Some approaches to Belief Bases Merge

In this work, we de fine some non-prioritized merge operators, that is, operators for the consistent union of belief bases. We de ne some postulates for several kinds of merge operator and we give different constructions: trivial merge, partial meet merge and kernel merge. For some constructions we provide representation theorems linking construction with a set of postulates. Finally, we propose that the formulated operators can be used in some multi-agent systemsVII Workshop de Agentes y Sistemas Inteligentes (WASI)Red de Universidades con Carreras en Informática (RedUNCI

Notions of relevance for modeling the dynamics of belief

We identify different kinds of relevance relations between formulas that emerge in the process of belief revision. Informal definitions for alternative notions of relevance are suggested and a set of schemas and intuitive postulates for formalizing these notions are proposed. The notions of relevance proposed here are shown to be good candidates for modeling the process of belief revision.Eje: Programación lógicaRed de Universidades con Carreras en Informática (RedUNCI

Tableau calculi for description logics revision

Focusing on the Ontology Change problem, we consider an environment where Description Logics (DLs) are the logical formalization to express knowledge bases, and the integration of distributed ontologies is developed under new extensions and modifications of the Belief Revision theories yielded originally in [2]. When using tableaux algorithms to reason about DLs, new information is yielded from the models considered in order to achieve knowledge satisfiability. Here a whole new theory have to be reinforced in order to adapt belief revision definitions and postulates to properly react over beliefs on extensions generated from these DL’s reasoning services. In this text we give a brief background of these formalisms and comment the research lines to be taken in our way to this goal.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI

Optimización de descomposiciones de esquemas normalizados en el modelo relacional

En este trabajo se presenta una optimización a los algoritmos de descomposición para obtener tercera forma normal y forma normal de Boyce-Codd [Date, 2001, Lewis et al., 2002, Maier, 1983, Silberschatz et al., 1999, Ullman, 1989]. Esta op- timización consiste en unir aquellos diferentes subesquemas obtenidos por los al- goritmos de descomposición tradicionales, obteniendo menos subesquemas, y por ende, probablemente menos reiteración de atributos. Esta optimización tiene la característica de preservar las propiedades de preservación de dependencias (en 3FN) y join sin pérdida (lossless join) a un bajo costo computacional ya que debe tomar los diferentes subesquemas compuestos por unos pocos atributos.Red de Universidades con Carreras en Informática (RedUNCI

Optimización de descomposiciones de esquemas normalizados en el modelo relacional

En este trabajo se presenta una optimización a los algoritmos de descomposición para obtener tercera forma normal y forma normal de Boyce-Codd [Date, 2001, Lewis et al., 2002, Maier, 1983, Silberschatz et al., 1999, Ullman, 1989]. Esta op- timización consiste en unir aquellos diferentes subesquemas obtenidos por los al- goritmos de descomposición tradicionales, obteniendo menos subesquemas, y por ende, probablemente menos reiteración de atributos. Esta optimización tiene la característica de preservar las propiedades de preservación de dependencias (en 3FN) y join sin pérdida (lossless join) a un bajo costo computacional ya que debe tomar los diferentes subesquemas compuestos por unos pocos atributos.Red de Universidades con Carreras en Informática (RedUNCI

Multiple Revision on Horn Belief Bases

In logic programming, Horn clauses play a basic role, and in many logical constructs their consideration is important. In this paper we study the multiple revision of a belief base where the underlying logic is composed by Horn clauses. The main di culties as to restricting to the Horn fragment for revision operators by a single sentence are analyzed, and general results are presented about multiple revision operators on belief bases. We de ne prioritized multiple revision operators under a more restricted logic than classical propositional logic, i.e. Horn logic. We propose a set of postulates and representation theorems for each operation. This work is relevant for multiple revision in areas that employ Horn clauses, such as logic programming and deductive databases applications.XVII Workshop Agentes y Sistemas Inteligentes (WASI).Red de Universidades con Carreras en Informática (RedUNCI

Towards a non monotonic description logics model

In order to deal with the Ontology Change problem and considering an environment where Description Logics (DLs) are used to describe ontologies, the question of how to integrate distributed ontologies appears to be in touch with Belief Revision since DL terminologies may define same concept descriptions of a not necessarily same world model. A possible alternative to reason about these concepts is to generate unique concept descriptions in a different terminology. This new terminology needs to be consistently created, trying to deal with the minimal change problem, and moreover, yielding a non-monotonic layer to express ontological knowledge in order to be further updated with new distributed ontologies.VII Workshop de Agentes y Sistemas Inteligentes (WASI)Red de Universidades con Carreras en Informática (RedUNCI

Revision of plausibility relations in dynamic systems

An agent recieves information from the environment which usually includes other agents. Sorne of those agents could be providers of data. It is natural for the agent to maintain a certain arder among the informants based on the reliability or plausibility they show. In a dynamic environment that arder might change. In this work we present a model for representing changes on plausibility relations. The central idea is that the beliefs of an agent are provided by a set of informants, for which there is a plausibility relation. This relation establishes if sorne informants are more reliable than others. We propase change operators for the plausibility relation. We give postulates for these operators and define their construction.I Workshop de Agentes y Sistemas Inteligentes (WASI)Red de Universidades con Carreras en Informática (RedUNCI