Formal Specification and Verification for Automated Production Systems

Complex industrial control software often drives safety- and mission-critical systems, like automated production plants or control units embedded into devices in automotive systems. Such controllers have in common that they are reactive systems, i.e., that they periodically read sensor stimuli and cyclically execute the same program to produce actuator signals. The correctness of software for automated production is rarely verified using formal techniques. Although, due to the Industrial Revolution 4.0 (IR4.0), the impact and importance of software have become an important role in industrial automation. What is used instead in industrial practice today is testing and simulation, where individual test cases are used to validate an automated production system. Three reasons why formal methods are not popular are: (a) It is difficult to adequately formulate the desired temporal properties. (b) There is a lack of specification languages for reactive systems that are both sufficiently expressive and comprehensible for practitioners. (c) Due to the lack of an environment model the obtained results are imprecise. Nonetheless, formal methods for automated production systems are well studied academically---mainly on the verification of safety properties via model checking. In this doctoral thesis we present the concept of (1) generalized test tables (GTTs), a new specification language for functional properties, and their extension (2) relational test tables (RTTs) for relational properties. The concept includes the syntactical notion, designed for the intuition of engineers, and the semantics, which are based on game theory. We use RTTs for a novel confidential property on reactive systems, the provably forgetting of information. Moreover, for regression verification, an important relational property, we are able to achieve performance improvements by (3) creating a decomposing rule which splits large proofs into small sub-task. We implemented the verification procedures and evaluated them against realistic case studies, e.g., the Pick-and-Place-Unit from the Technical University of Munich. The presented contribution follows the idea of lowering the obstacle of verifying the dependability of reactive systems in general, and automated production systems in particular for the engineer either by introducing a new specification language (GTTs), by exploiting existing programs for the specification (RTTs, regression verification), or by improving the verification performance

Formal techniques for the procedural control of industrial processes

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Programming Languages and Systems

This open access book constitutes the proceedings of the 31st European Symposium on Programming, ESOP 2022, which was held during April 5-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 21 regular papers presented in this volume were carefully reviewed and selected from 64 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Animation prototyping of formal specifications

At the present time one of the key issues relating to the design of real-time systems is the specification of software requirements. It is now clear that specification correctness is an essential factor for the design and implementation of high quality software. As a result considerable emphasis is placed on producing specifications which are not only correct, but provably so. This has led to the application of mathematically-based formal specification techniques in the software life-cycle model. Unfortunately, experience in safety-critical systems has shown that specification correctness is not, in itself, sufficient. Such specifications must also be comprehensible to all involved in the system development. The topic of this thesis—Animation Prototyping—is a methodology devised to make such specifications understandable and usable. Its primary objective is to demonstrate key properties of formal specifications to non-software specialists. This it does through the use of computer-animated pictures which respond to the dictates of the formal specification. [Continues.

Programming Languages and Systems

This open access book constitutes the proceedings of the 31st European Symposium on Programming, ESOP 2022, which was held during April 5-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 21 regular papers presented in this volume were carefully reviewed and selected from 64 submissions. They deal with fundamental issues in the specification, design, analysis, and implementation of programming languages and systems

Plethora : a framework for the intelligent control of robotic assembly systems

Plethora : a framework for the intelligent control of robotic assembly system

Safety Assurance in Interlocking Design

This thesis takes a pedagogical stance in demonstrating how results from theoretical computer science may be applied to yield significant insight into the behaviour of the devices computer systems engineering practice seeks to put in place, and that this is immediately attainable with the present state of the art. The focus for this detailed study is provided by the type of solid state signalling systems currently being deployed throughout mainline British railways. Safety and system reliability concerns dominate in this domain. With such motivation, two issues are tackled: the special problem of software quality assurance in these data-driven control systems, and the broader problem of design dependability. In the former case, the analysis is directed towards proving safety properties of the geographic data which encode the control logic for the railway interlocking; the latter examines the fidelity of the communication protocols upon which the distributed control system depends. The starting point for both avenues of attack is a mathematical model of the interlocking logic that is derived by interpreting the geographic data in process algebra. Thus, the emphasis is on the semantics of the programming language in question, and the kinds of safety properties which can be expressed as invariants of the system's ongoing behaviour. Although the model so derived turns out to be too concrete to be effectual in program verification in general, a careful analysis of the safety proof reveals a simple co-induction argument that leads to a highly efficient proof methodology. From this understanding it is straightforward to mechanise the safety arguments, and a prototype verification system is realised in higher-order logic which uses the proof tactics of the theorem prover to achieve full automation. The other line of inquiry considers whether the integrity of the overall design that coordinates the activities of many concurrent control elements can be compromised. Therefore, the formal model is developed to specifically answer safety-related concerns about the protocol employed to achieve distributed control in the management of larger railway networks. The exercise reveals that moderately serious design flaws do exist, but the real value of the mathematical model is twofold: it makes explicit one's assumptions about the conditions under which the faults can and cannot be activated, and it provides a framework in which to prove a simple modification to the design recovers complete security at negligible cost to performance