Component Substitution through Dynamic Reconfigurations

Component substitution has numerous practical applications and constitutes an active research topic. This paper proposes to enrich an existing component-based framework--a model with dynamic reconfigurations making the system evolve--with a new reconfiguration operation which "substitutes" components by other components, and to study its impact on sequences of dynamic reconfigurations. Firstly, we define substitutability constraints which ensure the component encapsulation while performing reconfigurations by component substitutions. Then, we integrate them into a substitutability-based simulation to take these substituting reconfigurations into account on sequences of dynamic reconfigurations. Thirdly, as this new relation being in general undecidable for infinite-state systems, we propose a semi-algorithm to check it on the fly. Finally, we report on experimentations using the B tools to show the feasibility of the developed approach, and to illustrate the paper's proposals on an example of the HTTP server.Comment: In Proceedings FESCA 2014, arXiv:1404.043

Debugging Process Algebra Specifications

International audienceDesigning and developing distributed and concurrent applications has always been a tedious and error-prone task. In this context, formal techniques and tools are of great help in order to specify such concurrent systems and detect bugs in the corresponding models. In this paper, we propose a new framework for debugging value-passing process algebra through coverage analysis. We illustrate our approach with LNT, which is a recent specification language designed for formally modelling concurrent systems. We define several coverage notions before showing how to instrument the specification without affecting original behaviors. Our approach helps one to improve the quality of a dataset of examples used for validation purposes, but also to find ill-formed decisions, dead code, and other errors in the specification. We have implemented a tool for automating our debugging approach, and applied it to several real-world case studies in different application areas

Formally Reasoning on a Reconfigurable Component-Based System --- A Case Study for the Industrial World

International audienceThe modularity offered by component-based systems made it one of the most employed paradigms in software engineering. Precise structural specification is a key ingredient that enables their verification and consequently their reliability. This gains special relevance for reconfigurable component-based systems. To this end, the Grid Component Model (GCM) provides all the means to define such reconfigurable component-based applications. In this paper we report our experience on the formal specification and verification of a reconfigurable GCM application as an industrial case study

Specification and verification of a dynamic reconfiguration protocol for agent-based applications

Theme 1 - Reseaux et systemes - Projet VASYSIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : 14802 E, issue : a.2001 n.4222 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Specification and Verification of a Dynamic Reconfiguration Protocol for Agent-Based Applications

Dynamic reconfiguration increases the availability of distributed applications by allowing them to evolve at run-time. This paper deals with the formal specification and model-checking verification of a dynamic reconfiguration protocol used in industrial agent-based applications. Starting from a reference implementation in Java, we produced a specification of the protocol using the Formal Description Technique LOTOS. We also specified a set of temporal logic formulas characterizing the correct behaviour of each protocol primitive. Finally, we studied various finite state configurations of the protocol, on which we verified these requirements using the CADP protocol engineering tool set

How To Touch a Running System

The increasing importance of distributed and decentralized software architectures entails more and more attention for adaptive software. Obtaining adaptiveness, however, is a difficult task as the software design needs to foresee and cope with a variety of situations. Using reconfiguration of components facilitates this task, as the adaptivity is conducted on an architecture level instead of directly in the code. This results in a separation of concerns; the appropriate reconfiguration can be devised on a coarse level, while the implementation of the components can remain largely unaware of reconfiguration scenarios. We study reconfiguration in component frameworks based on formal theory. We first discuss programming with components, exemplified with the development of the cmc model checker. This highly efficient model checker is made of C++ components and serves as an example for component-based software development practice in general, and also provides insights into the principles of adaptivity. However, the component model focuses on high performance and is not geared towards using the structuring principle of components for controlled reconfiguration. We thus complement this highly optimized model by a message passing-based component model which takes reconfigurability to be its central principle. Supporting reconfiguration in a framework is about alleviating the programmer from caring about the peculiarities as much as possible. We utilize the formal description of the component model to provide an algorithm for reconfiguration that retains as much flexibility as possible, while avoiding most problems that arise due to concurrency. This algorithm is embedded in a general four-stage adaptivity model inspired by physical control loops. The reconfiguration is devised to work with stateful components, retaining their data and unprocessed messages. Reconfiguration plans, which are provided with a formal semantics, form the input of the reconfiguration algorithm. We show that the algorithm achieves perceived atomicity of the reconfiguration process for an important class of plans, i.e., the whole process of reconfiguration is perceived as one atomic step, while minimizing the use of blocking of components. We illustrate the applicability of our approach to reconfiguration by providing several examples like fault-tolerance and automated resource control