Miguel Valero Espada

A State Space Distribution Policy Based on Abstract Interpretation

We aim at improving the performance of distributed algorithms for model checking and state space reduction. To this end, we introduce a new distribution policy of states over workers. This policy reduces the number of transitions between states located at different workers. This in turn is expected to reduce the communication costs of the distributed algorithms.The main idea is to use Abstract Interpretation techniques to compute a small approximation of the state space, starting from some high level description of the system. Based on this approximation, the connectivity of concrete states is predicted. This information is used to distribute states with expected connectivity to the same worker. Experiments show a considerable reduction of cross transitions, at the expense of a modest unbalance of nodes per worker.

Modal Abstractions in μCRL

We describe a framework to generate modal abstract approximations from process algebraic specifications, written in the language μCRL. We allow abstraction of state variables and action labels. Moreover, we introduce a new format for process specifications called Modal Linear Process Equation (MLPE). Every transition step may lead to a set of abstract tates labelled-with a set of abstract actions. We use MLPEs to characterize abstract interpretations of systems and to generate Modal Labelled Transition Systems, in which transitions may have two modalities may and must. We prove that the abstractions are sound for the full action-based μ-calculus. Finally, we apply the result to check some safety and liveness properties for the bounded retransmission protocol.

Formal Specification of JavaSpaces Architecture Using µCRL

We study a formal specification of the shared data space architecture, JavaSpaces. This Java technology provides a virtual space for entities, like clients and servers, to communicate by sharing objects. We use µCRL, a language that combines abstract data types with process algebra, to model an abstraction of this coordination architecture. Besides the basic primitives write, read and take, our model captures transactions and leasing. The main purpose of the proposed formalism is to allow the verification of distributed applications built under the JavaSpaces model. A simple case study is analyzed and automatically model checked using the µCRL and CADP tool sets.

Abstraction of parallel uniform processes with data

In practice, distributed systems are quite often composed by an arbitrarily large but finite number of processes that execute a similar program. Abstract interpretation is an effective technique to fight state explosion problems. In this paper, we propose a general framework for abstracting parallel composition of uniform processes with data, in the setting of a process algebraic language /spl mu/CRL We illustrate the feasibility of this technique by proposing two instances of the general framework and applying them to the verification of two systems.

An Abstract Interpretation Toolkit for μCRL

This paper describes a toolkit that assists in the task of generating abstract approximations of process algebraic specifications written in the language @mCRL. Abstractions are represented by Modal Labelled Transition Systems, which are mixed transition systems with may and must modalities. The approach permits to infer the satisfaction or refutation of safety and liveness properties expressed in the (action-based) @m-calculus. The tool supports the abstraction of states and action labels which allows to deal with infinitely branching systems.

Verification of JavaSpaces/spl trade/ parallel programs

We illustrate a formal verification method for distributed JavaSpaces applications by analyzing a nontrivial fault tolerant algorithm that solves a typical coordination problem. The problem consists of the computation of an extensive task, performed in parallel by splitting it into smaller and more manageable parts. The proposed solution, based on JavaSpaces coordination primitives, transactions and timeouts, is verified by translating it to the formal language /spl mu/CRL, together with the previously developed /spl mu/CRL-model of the JavaSpaces architecture, and by using model checking techniques.