Markus Roggenbach

A generic theorem prover of CSP refinement

We describe a new tool called Csp-Prover which is an interactive theorem prover dedicated to refinement proofs within the process algebra Csp. It aims specifically at proofs for infinite state systems, which may also involve infinite non-determinism. Semantically, Csp-Prover supports both the theory of complete metric spaces as well as the theory of complete partial orders. Both these theories are implemented for infinite product spaces. Technically, Csp-Prover is based on the theorem prover Isabelle. It provides a deep encoding of Csp. The tools architecture follows a generic approach which makes it easy to adapt it for various Csp models besides those studied here: the stable failures model

CSP-CASL: a new integration of process algebra and algebraic specification

\mathcal{F}

Algebraic–coalgebraic specification in CoCasl

and the traces model

Structured CSP: a process algebra as an institution

\mathcal{T}

Towards a unified view of bisimulation: a comparative study

.

Defining and model checking abstractions of complex railway models using CSP

CSP-CASL integrates the process algebra CSP [T. Hoare, Communicating Sequential Processes, Prentice-Hall, Englewood cliffs, NJ, 1985; A.W. Roscoe, The Theory and Practice of Concurrency, Prentice-Hall, Englewood cliffs, NJ, 1998] with the algebraic specification language CASL [P.D. Mosses (Ed.), CASL Reference Manual, Lecture Notes in Computer Science, Vol. 2960, Springer, Berlin, 2004; E. Astesiano, M. Bidoit, B. Krieg-Bruckner, H. Kirchner, P.D. Mosses, D. Sannella, A. Tarlecki, CASL--the common algebraic specification language, Theoret. Comput. Sci. 286 (2002) 153-196]. Its novel aspects include the combination of denotational semantics in the process part and, in particular, loose semantics for the data types covering both concepts of partiality and sub-sorting. Technically, this integration involves the development of a new so-called data-logic formulated as an institution. This data-logic serves as a link between the institution underlying CASL and the alphabet of communications necessary for the CSP semantics. Besides being generic in the various denotational CSP semantics, this construction leads also to an appropriate notion of refinement with clear relations to both data refinement in CASL and process refinement in CSP.

A complete axiomatic semantics for the CSP stable-failures model

We introduce CoCASL as a simple coalgebraic extension of the algebraic specification language CASL. CoCASL allows the nested combination of algebraic datatypes and coalgebraic process types. We show that the well-known coalgebraic modal logic can be expressed in COCASL. We present sufficient criteria for the existence of cofree models, also for several variants of nested cofree and free specifications. Moreover, we describe an extension of the existing proof support for CASL (in the shape of an encoding into higher-order logic) to COCASL.

Techniques for modelling and verifying railway interlockings

We introduce two institutions for the process algebra CSP, one for the traces model, and one for the stable failures model. The construction is generic and should be easily instantiated with further models. As a consequence, we can use structured specification constructs like renaming, hiding and parameterisation (that have been introduced over an arbitrary institution) also for CSP. With a small example we demonstrate that structuring indeed makes sense for CSP.

Towards a formal specification of an electronic payment system in CSP-CASL

Abstract The realm of approaches to operational descriptions and equivalences for concurrent systems in the literature lead to a series of different attempts to give a uniform characterization of what should be considered a bisimulation, mostly in an algebraic and/or categorical framework. Meanwhile the realm of such approaches calls itself for comparison and/or unification. We investigate how different abstract characterizations of bisimulations are related. In particular, we consider the coalgebraic approach of Aczel and Mendler, the observation structures (Kripke structures) of Degano, De Nicola and Montanari, the algebraic approach of Malacaria, the domain theoretic view of Abramsky and the categorical setting of Joyal, Nielsen and Winskel. The framework of Aczel and Mendler turns out to be the most general one in the sense that the other approaches can be translated into it. These translations, where the relation between the categorical setting of Joyal, Nielsen and Winskel with the coalgebraic approach is the most complicated one, enhance the understanding of the different approaches and contribute to a unified view of bisimulation.

Verification of Scheme Plans Using CSP

The safety analysis of interlocking railway systems involves verifying collision and derailment freedom. In this paper we propose a structured way of refining track plans, in order to expand track segments so that they form collections of track segments. We show how the abstract model can be model checked to ensure the safety properties, which must also hold in the corresponding concrete track plan, so that we will never need to model check the concrete track plan directly. We also identify the minimal number of trains that needs to be considered as part of the model checking, and we demonstrate the practicality of the approach on various scenarios.