Modal logics for reasoning about object-based component composition

Component-oriented development of software supports the adaptability and maintainability of large systems, in particular if requirements change over time and parts of a system have to be modified or replaced. The software architecture in such systems can be described by components and their composition. In order to describe larger architectures, the composition concept becomes crucial. We will present a formal framework for component composition for object-based software development. The deployment of modal logics for defining components and component composition will allow us to reason about and prove properties of components and compositions

Structural Refinement for the Modal nu-Calculus

We introduce a new notion of structural refinement, a sound abstraction of logical implication, for the modal nu-calculus. Using new translations between the modal nu-calculus and disjunctive modal transition systems, we show that these two specification formalisms are structurally equivalent. Using our translations, we also transfer the structural operations of composition and quotient from disjunctive modal transition systems to the modal nu-calculus. This shows that the modal nu-calculus supports composition and decomposition of specifications.Comment: Accepted at ICTAC 201

Automata games for multiple-model checking

3-valued models have been advocated as a means of system abstraction such that verifications and refutations of temporal-logic properties transfer from abstract models to the systems they represent. Some application domains, however, require multiple models of a concrete or virtual system. We build the mathematical foundations for 3-valued property verification and refutation applied to sets of common concretizations of finitely many models. We show that validity checking for the modal mu-calculus has the same cost (EXPTIME-complete) on such sets as on all 2-valued models, provide an efficient algorithm for checking whether common concretizations exist for a fixed number of models, and propose using parity games on variants of tree automata to efficiently approximate validity checks of multiple models. We prove that the universal topological model in [M. Huth, R. Jagadeesan, and D. A. Schmidt. A domain equation for refinement of partial systems. Mathematical Structures in Computer Science, 14(4):469-505, 5 August 2004] is not bounded complete. This confirms that the approximations aforementioned are reasonably precise only for tree-automata-like models, unless all models are assumed to be deterministic. © 2006 Elsevier B.V. All rights reserved

Interviews with the 2021 CONCUR Test-of-Time Award recipients

Last year, the CONCUR conference series inaugurated its Test-of-Time Award, purpose of which is to recognise important achievements in Con- currency Theory that were published at the CONCUR conference and that have stood the test of time. This year, the following four papers were chosen to receive the CONCUR Test-of-Time Awards for the periods 1994–1997 and 1996–1999 by a jury consisting of Rob van Glabbeek (chair), Luca de Alfaro, Nathalie Bertrand, Catuscia Palamidessi, and Nobuko Yoshida: - David Janin and Igor Walukiewicz. On the Expressive Completeness of the Propositional mu-Calculus with respect to Monadic Second Or- der Logic [3]. - Uwe Nestmann and Benjamin C. Pierce. Decoding Choice Encod- ings [4]. - Ahmed Bouajjani, Javier Esparza, and the late Oded Maler. Reacha- bility Analysis of Pushdown Automata: Application to Model- checking [2]. - Rajeev Alur, Thomas A. Henzinger, Orna Kupferman, and Moshe Y. Vardi. Alternating Refinement Relations [1]. This year, the second paper was live-interviewed by Nobuko Yoshida; the third paper was interviewed by Nathalie Bertrand and the forth paper was interviewed by Luca Aceto. Adam Barwell and Francisco Ferreira helped making the article from the live interview by Yoshida

Refinement sensitive formal semantics of state machines with persistent choice

Modeling languages usually support two kinds of nondeterminism, an external one for interactions of a system with its environment, and one that stems from under-specification as familiar in models of behavioral requirements. Both forms of nondeterminism are resolvable by composing a system with an environment model and by refining under-specified behavior (respectively). Modeling languages usually dont support nondeterminism that is persistent in that neither the composition with an environment nor refinements of under-specification will resolve it. Persistent nondeterminism is used, e.g., for modeling faulty systems. We present a formal semantics for UML state machines enriched with an operator persistent choice that models persistent nondeterminism. This semantics is based on abstract models - μ-automata with a novel refinement relation - and a sound three-valued satisfaction relation for properties expressed in the μ-calculus. © 2009 Elsevier B.V. All rights reserved