Interface Theories for (A)synchronously Communicating Modal I/O-Transition Systems

Interface specifications play an important role in component-based software development. An interface theory is a formal framework supporting composition, refinement and compatibility of interface specifications. We present different interface theories which use modal I/O-transition systems as their underlying domain for interface specifications: synchronous interface theories, which employ a synchronous communication schema, as well as a novel interface theory for asynchronous communication where components communicate via FIFO-buffers.Comment: In Proceedings FIT 2010, arXiv:1101.426

Verification of Modular Systems with Unknown Components Combining Testing and Inference

26 pagesVerification of a modular system composed of communicating components is a difficult problem, especially when the formal specifications, i.e., models of the components are not available. Conventional testing techniques are not efficient in detecting erroneous interactions of components because interleavings of internal events are difficult to reproduce in a modular system. The problem of detecting intermittent errors and other compositional problems in the absence of components' models is addressed in this paper. A method to infer a controllable approximation of communicating components through testing is elaborated. The inferred finite state models of components are used to detect compositional problems in the system through reachability analysis. To confirm a flaw in a particular component, a witness trace is used to construct a test applied to the component in isolation. The models are refined at each analysis step thus making the approach iterative

GRL: A Specification Language for Globally Asynchronous Locally Synchronous Systems

International audienceA GALS (Globally Asynchronous, Locally Synchronous) system consists of several synchronous subsystems that evolve concurrently and interact with each other asynchronously. Most formalisms and design tools support either the synchronous paradigm or the asynchronous paradigm but rarely combine both, which requires an intricate modeling of GALS systems. In this paper, we present a new language, called GRL (GALS Representation Language) designed to model GALS systems in an abstract and versatile manner for the purpose of formal verification. GRL has formal semantics combining the synchronous reactive model underlying dataflow languages and the asynchronous concurrent model underlying process algebras. We present the basic concepts and the main constructs of the language, together with an illustrative example

Stability of Asynchronously Communicating Systems

Recent software is mostly constructed by reusing and composing existing components. Software components are usually stateful and therefore described using behavioral models such as finite state machines. Asynchronous communication is a classic interaction mechanism used for such software systems. However, analysing communicating systems interacting asynchronously via reliable FIFO buffers is an undecidable problem. A typical approach is to check whether the system is bounded, and if not, the corresponding state space can be made finite by limiting the presence of communication cycles in behavioral models or by fixing buffer sizes. In this paper, we focus on infinite systems and we do not restrict the system by imposing any arbitrary bounds. We introduce a notion of stability and prove that once the system is stable for a specific buffer bound, it remains stable whatever larger bounds are chosen for buffers. This enables us to check certain properties on the system for that bound and to ensure that the system will preserve them whatever larger bounds are used for buffers. We also prove that computing this bound is undecidable but show how we succeed in computing these bounds for many typical examples using heuristics and equivalence checking

Compositional bisimulation metric reasoning with Probabilistic Process Calculi

We study which standard operators of probabilistic process calculi allow for compositional reasoning with respect to bisimulation metric semantics. We argue that uniform continuity (generalizing the earlier proposed property of non-expansiveness) captures the essential nature of compositional reasoning and allows now also to reason compositionally about recursive processes. We characterize the distance between probabilistic processes composed by standard process algebra operators. Combining these results, we demonstrate how compositional reasoning about systems specified by continuous process algebra operators allows for metric assume-guarantee like performance validation