Ismael Rodríguez

Using river formation dynamics to design heuristic algorithms

Finding the optimal solution to NP-hard problems requires at least exponential time. Thus, heuristic methods are usually applied to obtain acceptable solutions to this kind of problems. In this paper we propose a new type of heuristic algorithms to solve this kind of complex problems. Our algorithm is based on river formation dynamics and provides some advantages over other heuristic methods, like ant colony optimization methods. We present our basic scheme and we illustrate its usefulness applying it to a concrete example: The Traveling Salesman Problem.

Formal testing from timed finite state machines

In this paper we present a formal methodology to test both the functional and temporal behaviors in systems where temporal aspects are critical. We extend the classical finite state machines model with features to represent timed systems. Our formalism allows three different ways to express the timing requirements of systems. Specifically, we consider that time requirements can be expressed either by means of fix time values, by using random variables, or by considering time intervals. Different implementation relations, depending on both the interpretation of time and on the non-determinism appearing in systems, are presented and related. We also study how test cases are defined and applied to implementations. Test derivation algorithms, producing sound and complete test suites, are also presented. That is, by deriving these test suites we relate the different notions of passing tests and the different implementation relations. In other words, for a given correctness criterion, a system represents an appropriate implementation of a given model if and only if the system successfully passes all the test belonging to the derived test suite.

Extending EFSMs to Specify and Test Timed Systems with Action Durations and Time-Outs

In this paper, we introduce a timed extension of the extended finite state machines model. On one hand, we consider that (output) actions take time to be performed. This time may depend on several factors, such as the value of variables. On the other hand, our formalism allows us to specify time-outs. In addition to presenting our language, we develop a testing theory. First, we define 10 timed conformance relations and relate them. Second, we introduce a notion of timed test and define how to apply tests to implementations. Finally, we give an algorithm to derive sound and complete test suites with respect to the implementation relations presented in the paper. This paper represents an extended and improved version of [1].

HOTL: Hypotheses and observations testing logic☆

El proyecto realizado consiste en la implementacion de una herramienta capaz de simular el comportamiento descrito en una logica desarrollada (HOTL: Hypotheses and observations testing logic), en un excelente trabajo de investigacion, por parte de nuestro profesor director de proyecto D. Ismael Rodriguez Laguna y sus dos companeros D. Manuel Nunez y Dna. Mercedes G. Merayo. La implementacion ha sido integrada en una interfaz grafica que nos permitira ejecutar una seria de reglas definidas en la logica dado un modelo, y dadas una especificacion concreta, unas observaciones y unas hipotesis y la aplicacion de las reglas sobre estos elementos, nos diga si la implementacion es conforme o no respecto de la especificacion. Todo esto mostrandose de manera grafica para que el usuario sea consciente de lo ocurrido en cada momento, como por ejemplo; la carga de la especificacion, de las observaciones e hipotesis, los modelos generados a partir de las observaciones, la generacion de modelos que implica la ejecucion de las reglas una a una, etc. La herramienta ha sido implementada sobre una plataforma Java y su diseno se ha realizado llevando a cabo tecnicas y metodos empleados en ingenieria del software, tales como un arquitectura clara de la aplicacion (que facilitara la ampliacion futura de la herramienta), uso de patrones de diseno, division del trabajo en iteraciones, etc., ademas del uso de conocimientos de metodologia y tecnologia de la programacion para el desarrollo de ciertos algoritmos necesarios para la implementacion de la logica.[ABSTRACT]The made project consists of the implementation of a tool able to simulate the behavior described in a developed logic (HOTL: Hypotheses and observations testing logic), in an excellent work of investigation, on the part of our professor director of project D. Ismael Rodriguez Laguna and their two companions D. Manuel Nunez and Dna. Mercedes G. Merayo.[ABSTRACT] The implementation has been integrated in a graphical interface that will allow us to execute serious of rules defined in the given logic a model, and given a concrete specification, observations and a hypothesis and the application of the rules on these elements, says to us if the implementation is in agreement or nonrespect to the specification. All this being of graphical way so that the user is conscious of the happened thing at every moment, like for example; the load of the specification, the observations and hypothesis, the models generated from the observations, the generation of models that the execution of rules one to one implies, etc. The tool has been implemented on a Java platform and its technical design has been made carrying out and used methods in engineering of the software, such as a clear architecture of the application (that it will facilitate the future extension of the tool), use of design patterns, division of the work in iterations, etc., in addition to the use of knowledge of methodology and technology of the programming for the development of certain necessary algorithms for the implementation of the logic.

PAMR: A Process Algebra for the Management of Resources in Concurrent Systems

In this paper we present a process algebra for the management of resources in concurrent systems. Our aim is to define a formal framework that can help in the task of specifying systems that depend, for their execution, on a set of resources that they use. Usually systems consist in a set of processes. In order to improve their performance, these processes will be able to exchange resources among them. In our language, processes will consist in a behavior (formalized as a LOTOS process) and in information about the resources that they own. Systems will be defined as the parallel composition of a set of processes. We will study some examples applying the features of PAMR. These examples will try to show the usefulness of our language for specifying and analyzing concurrent systems where resources play an important role.

Specification, testing and implementation relations for symbolic-probabilistic systems

We consider the specification and testing of systems where probabilistic information is not given by means of fixed values but as intervals of probabilities. We will use an extension of the finite state machines model where choices among transitions labelled by the same input action are probabilistically resolved. We will introduce our notion of test and we will define how tests are applied to implementations under test. We will also present implementation relations to assess the conformance, up to a level of confidence, of an implementation to a specification. In order to define these relations we will take finite samples of executions of the implementation and compare them with the probabilistic constraints imposed by the specification. Finally, we will give an algorithm for deriving sound and complete test suites.

Towards Testing Stochastic Timed Systems

In this paper we present a first approach to the definition of conformance testing relations for systems presenting stochastic timed behavior. By stochastic time we mean that the probability of performing an event may vary according to the elapsed time. In particular, we will consider delays specified by means of random variables.

Finding Minimum Spanning/Distances Trees by Using River Formation Dynamics

River Formation Dynamics(RFD) is an heuristic method similar to Ant Colony Optimization(ACO). In fact, RFD can be seen as a gradient version of ACO, based on copying how water forms rivers by eroding the ground and depositing sediments. As water transforms the environment, altitudes of places are dynamically modified, and decreasing gradients are constructed. The gradients are followed by subsequent drops to create new gradients, reinforcing the best ones. By doing so, good solutionsare given in the form of decreasingaltitudes. We apply this method to solve two NP-complete problems, namely the problems of finding a minimum distances treeand finding a minimum spanning treein a variable-cost graph. We show that the gradient orientation of RFD makes it specially suitable for solving these problems, and we compare our results with those given by ACO.

Specification and testing of autonomous agents in e-commerce systems†

This paper presents a generic formal framework to specify and test autonomous e‐commerce agents. First, the formalism to represent the behaviour of agents is introduced. The corresponding machinery to define how implementations can be tested follows. Two testing approaches are considered. The first of them, which can be called active, is based on stimulating the implementation under test (IUT) with a test. The peculiarity is that tests will be defined as a special case of autonomous e‐commerce agent. The second approach, which can be called passive, consists of observing the behaviour of the tested agent in an environment containing other agents. As a case study the framework is applied to the e‐commerce system Kasbah. Copyright

Encoding PAMR into (Timed) EFSMs

In this paper we show how the formal framework introduced in PAMR (Process Algebra for the Management of Resources) can be included into a notion of Extended Finite State Machines (in short EFSM). First, we give the definition of process. Following the lines of PAMR, a process consists not only of information about its behavior but also of information about the preference for resources. This information will be encoded into a model based on EFSMs. In contrast with the original definition of PAMR, a notion of time is included in our processes, that is, transitions take time to be performed. Systems are defined as the composition of several processes. We present different implementation relations, depending on the interpretation of time, and we relate them. Finally, we study how tests cases are defined and applied to implementations.