D23 ProB

Improved Kernel to deal with large sets and relations

In this part we describe the successful application of the ProB validation tool on an industrial case study. The case study centres on the San Juan metro system installed by Siemens. The control software was developed and formally proven with B. However, the development contains certain assumptions about the actual rail network topology which have to be validated separately in order to ensure safe operation. For this task, Siemens has developed custom proof rules for AtelierB. AtelierB, however, was unable to deal with about 80 properties of the deployment (running out of memory). These properties thus had to be validated by hand at great expense (and they need to be revalidated whenever the rail network infrastructure changes). In this paper we show how we were able to use ProB to validate all of the about 300 properties of the San Juan deployment, detecting exactly the same faults automatically in around 17 minutes that were manually uncovered in about one man-month. This achievement required the extension of the ProB kernel for large sets as well as an improved constraint propagation phase. We also outline some of the effort and features that were required in moving from a tool capable of dealing with medium-sized examples towards a tool able to deal with actual industrial specifications. Notably, a new parser and type checker had to be developed. We also touch upon the issue of validating ProB, so that it can be integrated into the SIL4 development chain at Siemens

Michael Leuschel, Jérôme Falampin, Fabian Fritz, Daniel Plagge, Automated Property Verification for Large Scale B Models, FM'2009.

Multi-Level Animation and Validation

We provide a detailed description of refinement in Event-B, both as a contribution in itself and as a foundation for the approach to simultaneous animation of multiple levels of refinement that we propose. We present an algorithm for simultaneous multi-level animation of refinement, and show how

it can be used to detect a variety of errors that occur frequently when using refinement.

The algorithm has been implemented in ProB and we applied it to several case studies, showing that multi-level animation is tractable also on larger models.

Refinement-Animation for Event-B --- Towards a Method of Validation. ABZ'2010

Test-Case Generation

Choreography models describe the communication protocols between services. Testing of service choreographies is an important task for the quality assurance of service-based systems as used e.g. in the context of service-oriented architectures (SOA). The formal modeling of service choreographies enables a model-based integration testing (MBIT) approach. We present MBIT methods for our service choreography modeling approach called Message Choreography Models (MCM). For the model-based testing of service choreographies, MCMs are translated into Event-B models and used as input for our test generator which uses the model checker ProB.

Sebastian Wieczorek, Vitaly Kozyura, Andreas Roth, Michael Leuschel, Jens Bendisposto, Daniel Plagge, Ina Schieferdecker. Applying Model Checking to Generate Model-based Integration Tests from Choreography Models. TESTCOM/FATES 2009.

Proof-Directed Model Checking

With the aid of the ProB Plugin, the Rodin Platform provides an integrated environment for editing, proving, animating and model checking Event-B models. This is of considerable benefit to the modeler, as it allows him to switch between the various tools to validate, debug and improve his or her models. The crucial idea of this paper is that the integrated platform also provides benefits to the tool developer, i.e., it allows easy access to information from other tools. Indeed, there has been considerable interest in combining model checking, proving and testing. In previous work we have already shown how a model checker can be used to complement the Event-B proving environment, by acting as a disprover. In this paper we show how the prover can help improve the efficiency of the animator and model checker.

Jens Bendisposto, Michael Leuschel. Proof Assisted Model Checking for B. ICFEM 2009.

Inspection of Alternate Approaches

ProB is a model checker for high-level B and Event-B models based on constraint-solving. In this paper we investigate alternate approaches for validating high-level B models using alternative techniques and tools based on using BDDs, SAT-solving and SMT-solving. In particular, we examine whether PROB can be complemented or even supplanted by using one of the tools BDDBDDB, Kodkod or SAL.

Daniel Plagge, Michael Leuschel, Ilya Lopatkin, Alexander Romanovsk. SAL, Kodkod, and BDDs for Validation of B Models. Lessons and Outlook. AFM'09.

Validation of ProB

Symmetry reduction is a model checking technique that can help alleviate the problem of state space explosion, by preventing redundant state space exploration. In previous work, we have developed three effective approaches to symmetry reduction for B that have been implemented into the ProB model checker, and we have proved the soundness of our state symmetries. However, it is also important to show our techniques are sound with respect to standard model checking, at the algorithmic level. In this paper, we present a retrospective B development that addresses this issue through a series of B refinements. This work also demonstrates the valuable insights into a system that can be gained through formal modelling.

Edd Turner, Michael Butler, Michael Leuschel. A Refinement-Based Correctness Proof of Symmetry Reduced Model Checking. ABZ'2010.