Foundations of the B method

B is a method for specifying, designing and coding software systems. It is based on Zermelo-Fraenkel set theory with the axiom of choice, the concept of generalized substitution and on structuring mechanisms (machine, refinement, implementation). The concept of refinement is the key notion for developing B models of (software) systems in an incremental way. B models are accompanied by mathematical proofs that justify them. Proofs of B models convince the user (designer or specifier) that the (software) system is effectively correct. We provide a survey of the underlying logic of the B method and the semantic concepts related to the B method; we detail the B development process partially supported by the mechanical engine of the prover

imAgent: un soporte para la simulación de sistemas de agentes móviles sobre Ns

En los últimos años, el paradigma de agentes móviles ha recibido una creciente atención por parte de los investigadores. Esta actividad se ha cristalizado en el desarrollo de una variedad de sistemas de soporte para agentes móviles, y trabajos de normalización que permitirán el desarrollo de sistemas comerciales. Sin embargo, en este aspecto no se ha logrado aún la difusión esperada de tales sistemas. Se argumenta que esta situación se debe principalmente a la falta de resultados cuantitativos que inciten a los desarrolladores a adoptar esta tecnología.Palabras clave: agentes móviles, simulació

Distributed Directory Service and Message Routing for Mobile Agents

Research about networks and agents has identified the need for a layer that provides a uniform protocol to communicate with fixed and mobile agents. In order to preserve the compatibility with existing infrastructures, proposed solutions have involved a "home agent", which forwards messages to a mobile entity. The mechanism of a home agent puts a burden on the infrastructure, which may hamper the scalability of the approach, in particular, in massively distributed systems, such as the amorphous computer or the ubiquitous/pervasive computing environment. Free from any compatibility constraint, we have designed an algorithm to route messages to mobile agents that does not require any fixed location. The algorithm has two different facets: a distributed directory service that maintains distributed information about the location of a mobile agent, and a message router that uses the directory service to deliver messages to a mobile agent. Two properties of the algorithm were established. The safety property ensures that messages are delivered to the agent they were aimed at, whereas the liveness property guarantees that messages eventually get delivered. A mechanical proof of the properties was carried out using the proof assistant Coq

Distributed Directory Service and Message Routing for Mobile Agents

Research about networks and agents has identied the need for a layer that provides a uniform protocol to communicate with xed and mobile agents. In order to preserve the compatibility with existing infrastructures, proposed solutions have involved a \home agent", which forwards messages to a mobile entity. The mechanism of a home agent puts a burden on the infrastructure, which may hamper the scalability of the approach, in particular, in massively distributed systems, such as the amorphous computer or the ubiquitous/pervasive computing environment. Free from any compatibility constraint, we have designed an algorithm to route messages to mobile agents that does not require any xed location. The algorithm has two dierent facets: a distributed directory service that maintains distributed information about the location of a mobile agent, and a message router that uses the directory service to deliver messages to a mobile agent. Two properties of the algorithm were establi..