Experience in developing the mCRL2 toolset

mCRL2 is a language with a toolset for formal analysis of behaviour of concurrent systems. It is developed in an academic research group to support process algebra based verification in an academic as well as an industrial setting. This paper provides an insight into the experiences and practises in developing and maintaining the mCRL2 toolset

Experiences with formal engineering: model-based specification, implementation and testing of a software bus at Neopost

We report on the actual industrial use of formal methods during the development of a software bus. During an internship at Neopost Inc., of 14 weeks, we developed the server component of a software bus, called the XBus, using formal methods during the design, validation and testing phase: we modeled our design of the XBus in the process algebra mCRL2, validated the design using the mCRL2-simulator, and fully automatically tested our implementation with the model-based test tool JTorX. This resulted in a well- tested software bus with a maintainable architecture. Writing the model (mdev), simulating it, and testing the implementation with JTorX only took 17% of the total development time. Moreover, the errors found with model-based testing would have been hard to find with conventional test methods. Thus, we show that formal engineering can be feasible, beneficial and cost-effective.\ud The findings above, reported earlier by us in (Sijtema et al., 2011) [1], were well- received, also in industrially oriented conferences (Ferreira and Romanenko, 2010) [2] and [3]. In this paper, we look back on the case study, and carefully analyze its merits and shortcomings. We reflect on (1) the added benefits of model checking, (2) model completeness and (3) the quality and performance of the test process.\ud Thus, in a second phase, after the internship, we model checked the XBus protocol—this was not done in [1] since the Neopost business process required a working implementation after 14 weeks. We used the CADP tool evaluator4 to check the behavioral requirements obtained during the development. Model checking did not uncover errors in model mdev, but revealed that model mdev was neither complete nor optimized: in particular, requirements to the so-called bad weather behavior (exceptions, unexpected inputs, etc.) were missing. Therefore, we created several improved models, checked that we could validate them, and used them to analyze quality and performance of the test process. Model checking was expensive: it took us approx. 4 weeks in total, compared to 3 weeks for the entire model-based testing approach during the internship.\ud In the second phase, we analyzed the quality and performance of the test process, where we looked at both code and model coverage. We found that high code coverage (almost 100%) is in most cases obtained within 1000 test steps and 2 minutes, which matches the fact that the faults in the XBus were discovered within a few minutes.\ud Summarizing, we firmly believe that the formal engineering approach is cost-effective, and produces high quality software products. Model checking does yield significantly better models, but is also costly. Thus, system developers should trade off higher model quality against higher costs

Bridging formal models : an engineering perspective

The thesis presents different techniques that can be used to build formal behavioral models. If modal properties are formulated, the models can be subjected to verification techniques to determine whether a model possesses the desired properties. However many native environments do not facilitate tools or techniques to verify them. Hence, these models need to be transformed into other models that provide suitable techniques for a formal analysis. The transformations are classified into two engineering approaches, namely syntactically engineered models and semantically engineered models. Syntactically engineered models are constructed from input specifications without explicitly considering the semantics. Semantically engineered models are constructed from input specifications by explicitly considering the semantics. The syntactic engineering approach presents four dedicated modeling techniques that construct or disseminate verification results for formal models. The first modeling technique describes a way to create models from system descriptions that specify concurrent behavior. Here, we model three variations of a 2×2 switch, for which the models are subsequently compared to models created in the specification languages: TLA+, Bluespec, Statecharts, and ACP. The comparison validates that mCRL2 is a suitable specification language to model descriptions or specify the behavior for prototype systems. The second syntactic technique constructs an mCRL2 model from a software implementation that operates a printer for printing Printed Circuit Boards. The model is used to advise (other) software engineers on dangerous language constructs in the control software. Hence, the model is model checked for various safety properties. The implementation is modeled through an over-approximation on the behavior by abstracting from program variables, such that only interface calls between processes and non-deterministic choices in procedures remain. The third modeling technique describes a language transformation from the language Chi 2.0 language to the mCRL2 language. The purpose of the transformation is to facilitate model checking techniques to the discrete part of the Chi 2.0 language

Formal development of control software in the medical systems domain

In this thesis we describe the effectiveness of applying a number of formal techniques to the development of industrial control software at Philips Healthcare. We demonstrate how these techniques were tightly incorporated to the industrial workflow and the issues encountered during the application. The work was established in an industrial context, dealing with real industrial projects and a real product concerning the development of interventional X-ray systems. The results are very conclusive in the sense that the used formal techniques could deliver substantially better quality code compared to the code developed in conventional development methods. Also, the results show that the productivity of the formally developed code is better than the productivity of code developed by projects at Philips Healthcare or projects reported worldwide. The thesis also includes a number of design and specification guidelines that assist constructing verifiable components using model checking. The guidelines were successful in designing and verifying a controller component developed at Philips Healthcare. Hence, the guidelines can provide an effective framework to design verifiable control components in industrial settings

Tools and Algorithms for the Construction and Analysis of Systems

This book is Open Access under a CC BY licence. The LNCS 11427 and 11428 proceedings set constitutes the proceedings of the 25th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2019, which took place in Prague, Czech Republic, in April 2019, held as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2019. The total of 42 full and 8 short tool demo papers presented in these volumes was carefully reviewed and selected from 164 submissions. The papers are organized in topical sections as follows: Part I: SAT and SMT, SAT solving and theorem proving; verification and analysis; model checking; tool demo; and machine learning. Part II: concurrent and distributed systems; monitoring and runtime verification; hybrid and stochastic systems; synthesis; symbolic verification; and safety and fault-tolerant systems

Bringing Model Checking Closer To Practical Software Engineering

Bal, H.E. [Promotor]Templon, J.A. [Copromotor]Willemse, T.A.C. [Copromotor