Negation-as-failure considered harmful

In logic programs, negation-as-failure has been used both for representing negative information and for providing default nonmonotonic inference. In this paper we argue that this twofold role is not only unnecessary for the expressiveness of the language, but it also plays against declarative programming, especially if further negation symbols such as strong negation are also available. We therefore propose a new logic programming approach in which negation and default inference are independent, orthogonal concepts. Semantical characterization of this approach is given in the style of answer sets, but other approaches are also possible. Finally, we compare them with the semantics for logic programs with two kinds of negation.Red de Universidades con Carreras en Informática (RedUNCI

Representing generalization relationships in logic programming

Modeling is one of the most important activities throughout any software development life cycle. Within object-oriented modeling, class generalization is a powerful, yet simple concept for abstracting commonalities between classes. Although, as classes evolved in the model, their semantics may become inconsistent with previous generalization relationships. Automated tools are necessary in order to preserve model coherence. In this paper we present a logic programming translation of several kinds of class hierarchies, in order to be used in the process of automated model checking. This representation includes positive and negative information, and preserves individual class properties. Thus, the resulting program is not affected with changes in class semantics or in the hierarchies.Eje: Lógica e Inteligencia artificialRed de Universidades con Carreras en Informática (RedUNCI

The SEWASIE architecture: a multi-agent system for data integration

In this paper we present the SEWASIE system, a multi-level agent-based architecture for querying heterogeneous data sources integrated by means of ontologies. Main features of this system are: two level data integration scheme, a query tool that supports the user in formulating a precise query, integrated tools for negotiation and information monitoring, and an agent infrastructure that provides a unifying framework for the architecture. In this work we focus on the agent infrastructure, from the user interface to the query answering mechanismEje: VI Workshop de Agentes y Sistemas Inteligentes (WASI)Red de Universidades con Carreras en Informática (RedUNCI

The multi-agent system architecture in SEWASIE

We describe the design, implementation and deployment of the multi-level agent-based system architecture developed for the SEWASIE project. The aim of the system is to help the user in querying heterogeneous data sources which are integrated by means of ontologies. The agent architecture is based on a two level data integration scheme supported by mediators and brokers, connected by a peer to peer mechanism. Implementation is done on top of the JADE system, a modular and scalable platform that satisfies FIPA standards.Facultad de Informátic

Checking semantics in UML models: use cases diagrams

Constraints add to the semantics to UML models in the form of statements which are expected to hold for the model to be considered correct, i.e., to satisfy system requirements. Constraints are considered in the UML metamodel as adornments attached to model elements, and languages like OCL allow for different statements to be expressed. Despite several CASE-like tools are currently supporting UML diagram and constraint definition, as far as we know none of them provides support for verification and maintainance of constraint consistency. Having this kind of facility helps users in the design of UML models, specially when these models are complex and the impact of model evolution is difficult to trace. This work studies how constraint consistency may be compromised when model elements are introduced or modified during system development. Focus is over use case diagrams, which suffice to highlight a number of important issues related with consistency maintenance. We introduce procedures for verifying and maintaining constraint consistency, and illustrate them using a simple constraint specification language. Our goal is to make a first step in the development of tools for automatic verification and mantainance of model semantics.Eje: Ingeniería de softwareRed de Universidades con Carreras en Informática (RedUNCI

A framework for defining and checking constraints in requirement gathering and definition

Requirements capture user needs about a system [KG99]. They stand for those functional and nonfunctional attributes the system must posses to be considered correct. Requirements also dictate how the system should respond to user interaction. Therefore, they play a very important role in software development. They state what the system should do for the user to be satisfied, and therefore they lead all development stages in the lifecycle. They are used to communicate user needs to all people involved in the development process, the system architecture is built upon them and the testing stage uses them as satisfaction criteria.Eje: Ingeniería de Software y Base de DatosRed de Universidades con Carreras en Informática (RedUNCI

Checking semantics in UML models

Modeling is one of the most crucial activities during all the phases in any software development life cycle. Typically, system development is a very complex task, and working with models helps to handle this complexity in an organized way, allowing us to reason about the properties that entities possess. In software engineering, notation, techniques and methodology for object-oriented model building has been lately the focus of active research work. In the case of object-oriented software development, models are composed by a number of communicating and well delimited elements. Although such models are sometimes harder to develop, they are easier to understand, and simpler to maintain and modify.Thus, reusability of elements among models is enhanced. In order to maximize these properties, we need tools that support the process of object- oriented development by serving as repository of previously asserted knowledge, checking the integrity of the model and maintaining the different views that form each model. Consequently, it is expected this automatic control will reduce the manual, error-prone work of maintaining model consistency across all life cycle phases. UML, Unified Modeling Language is a graphical language for visualizing, specifying, constructing and documenting the elements of a software intensive system. UML provides notation for expressing the model, in the form of graphic and text elements. Attached to these elements, there is a semantic interpretation that attempts to capture the meaning of the model, and it is represented by the constraint mechanism. Constraints are one of the three extensibility mechanisms that UML introduces, although currently the language for expressing them is not standard (natural language or OCL can be used for this purpose). Supporting tools for object oriented development in UML should not only provide a graphic editor for the notation, but also help to ensure the coherence of its semantics aspects. This research line attempts to formalize the consistency check process in UML models.Eje: Ingeniería de SoftwareRed de Universidades con Carreras en Informática (RedUNCI

Un análisis sobre la lógica difusa como herramienta para la representación de conocimiento

El estudio y las aplicaciones de la lógica difusa han tenido en los últimos años un gran desarrollo. Sin embargo, se ha generado una polémica acerca de sus propiedades como herramienta para la Representación de Conocimiento. En este trabajo se presenta una clasificación de distintos sistemas de lógica difusa desde el punto de vista de un sistema formal, y en base a ello se estudian sus propiedades metalógicas. Esto permite analizar formalmente aspectos relevantes de distintos sistemas de Lógica Difusa en el campo de la Representación de Conocimiento dentro de la Inteligencia Artificial. Finalmente, se enumeran algunas posibles aplicaciones en este área.Eje: 2do. Workshop sobre aspectos teóricos de la inteligencia artificialRed de Universidades con Carreras en Informática (RedUNCI

Negation-as-failure considered harmful

In logic programs, negation-as-failure has been used both for representing negative information and for providing default nonmonotonic inference. In this paper we argue that this twofold role is not only unnecessary for the expressiveness of the language, but it also plays against declarative programming, especially if further negation symbols such as strong negation are also available. We therefore propose a new logic programming approach in which negation and default inference are independent, orthogonal concepts. Semantical characterization of this approach is given in the style of answer sets, but other approaches are also possible. Finally, we compare them with the semantics for logic programs with two kinds of negation.Red de Universidades con Carreras en Informática (RedUNCI

Lenguajes para intercambio de reglas en la web semántica

El objetivo general de la investigación es la representación y el uso del conocimiento en sistemas computacionales, para lo cual es necesario desarrollar métodos eficientes para la representación, y mecanismos de razonamiento confiables que permitan su procesamiento. Para ser eficiente, la representación del conocimiento debe ser a la vez compacta y comprensible. Para ser confiable, el mecanismo de razonamiento debe no sólo ser exacto sino también intuitivo y computacionalmente tratable a la vez. El estudio de los formalismos que tienen estos objetivos aparentemente contradictorios involucra aspectos tantos teóricos como tecnológicos. Actualmente surge un renovado inter´es en estos temas debido a la necesidad emergente de compartir, actualizar y combinar el conocimiento de sistemas computacionales pre existentes.Eje: Agentes y Sistemas InteligentesRed de Universidades con Carreras en Informática (RedUNCI