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

Tau Be or not Tau Be? - A Perspective on Service Compatibility and Substitutability

One of the main open research issues in Service Oriented Computing is to propose automated techniques to analyse service interfaces. A first problem, called compatibility, aims at determining whether a set of services (two in this paper) can be composed together and interact with each other as expected. Another related problem is to check the substitutability of one service with another. These problems are especially difficult when behavioural descriptions (i.e., message calls and their ordering) are taken into account in service interfaces. Interfaces should capture as faithfully as possible the service behaviour to make their automated analysis possible while not exhibiting implementation details. In this position paper, we choose Labelled Transition Systems to specify the behavioural part of service interfaces. In particular, we show that internal behaviours (tau transitions) are necessary in these transition systems in order to detect subtle errors that may occur when composing a set of services together. We also show that tau transitions should be handled differently in the compatibility and substitutability problem: the former problem requires to check if the compatibility is preserved every time a tau transition is traversed in one interface, whereas the latter requires a precise analysis of tau branchings in order to make the substitution preserve the properties (e.g., a compatibility notion) which were ensured before replacement.Comment: In Proceedings WCSI 2010, arXiv:1010.233

Formalization of Component Substitutability

AbstractComponent-Based Software Engineering (CBSE) is increasingly used to develop large scale software. In this context, a complex software is composed of many software components which are developed independently and which are considered as black boxes. Furthermore, they are assembled and often dependent from each other. In this setting, component upgrading is a key issue, since it enables software components to evolve. To support component upgrading, we have to deal with component dependencies which need to be expressed precisely. In this paper, we consider that component upgrade requires managing substitutability between the new and the old components. The substitutability check is based on dependency and context descriptions. It involves maintaining the availability of previously used services, while making sure that the effect of the new provided services do not disrupt the system and the context invariants are still preserved. We present here a formal definition and a verification algorithm for safe component substitutability

Formal aspects of component software

This is the pre-proceedings of 6th International Workshop on Formal Aspects of Component Software (FACS'09)

Consistent Substitution of Object in Rule-based IoT Applications

International audienceThe Internet of Things (IoT) is a network of physical devices and software entities that interact together for fulfilling an overall objective. Such applications are built by selecting and composing several objects. Recent frameworks promote the use of 'if event(s) then action(s)' rules to make explicit the way these objects interact together, i.e., if an event is raised, then an action is triggered. IoT applications are not monolithic applications built once and for all. In this paper, we focus on the replacement of an object, operation which is often required for substituting an out-of-order or obsolete device. When substituting an object by another one, the user may want the application to provide at least the same functionalities as before. Therefore, replacement should be supported by automated techniques and tools in order to guarantee the preservation of the application behaviour. As a result, we first define several notions of object substitution. Then, we show how these notions can be automatically checked or computed. Finally, we present the tool support and its integration to the Mozilla WebThings platform for applying our approach on smart home applications

Service substitution : a behavioral approach based on Petri Nets

Service-Oriented Computing is an emerging computing paradigm that supports the modular design of (software) systems. Complex systems are designed by composing less complex systems, called services. Such a (complex) system is a distributed application often involving several cooperating enterprises. As a system usually changes over time, individual services will be substituted by other services. Substituting one service by another one should not affect the correctness of the overall system. Assuring correctness becomes particularly challenging, as the services rely on each other, and each of the involved enterprises only oversees a part of the overall system. In addition, services communicate asynchronously which makes the analysis even more difficult. For this reason, formal methods to support service substitution are indispensable. In this thesis, we study service substitution at the level of service models. Thereby we restrict ourselves to service behavior. As a formalism to model service behavior, we use Petri nets. The first contribution of this thesis is the definition of several substitutability criteria that are suitable in the context of Service-Oriented Computing. Substituting a service S by a service S0 should preserve some behavioral properties of the overall system. For each set of behavioral properties and a given service S, there exists a set of behaviorally compatible services for S. A substitutability criterion defines which of these behaviorally compatible services of S have to be preserved by S0. We relate our substitutability criteria to preorders and equivalences known from process theory. The second contribution of this thesis is to present, for each substitutability criterion, a procedure to decide whether a service S0 can substitute a service S. The decision requires the comparison of the in general infinite sets of behaviorally compatible services for the services S and S0. Hence, we extend existing work on an abstract representation of all behaviorally compatible services for a given service. For each notion of behavioral compatibility, we present an algorithmic solution to represent all behaviorally compatible services. Based on these representations, we can decide substitutability of a service S by a service S0. The third contribution of this thesis is a method to support the design of a service S0 that can substitute a service S according to a substitutability criterion. Our approach is to derive a service S0 from the service S by stepwise transformation. To this end, we present several transformation rules. Finally, we formalize and we extend the equivalence notion for services specified in the language WS-BPEL. That way, we demonstrate the applicability of our work

Unifying Architectural and Behavioural Specifications of Distributed Components

International audienceWe present a novel specification language called JDC to be used at design phase of distributed components. The extensive seek for asynchrony in distributed components demands new techniques for its specification that have not been addressed before. We propose to focus the specification on its data-flow; this allows to reason about inter-component synchronisations produced by a data-driven synchronisation model. The language is endowed with enough formality so it allows a constructive approach; it allows the generation of behaviour models which can be model-checked, and the generation of code skeletons with the control flow of components. Globally, this approach aims at generating components with strong guarantees w.r.t. their behaviour