Arne Skou

Bisimulation through probabilistic testing

Abstract We propose a language for testing concurrent processes and examine its strength in terms of the processes that are distinguished by a test. By using probabilistic transition systems as the underlying semantic model, we show how a testing algorithm can distinguish, with a probability arbitrarily close to one, between processes that are not bisimulation equivalent. We also show a similar result (in a slightly stronger form) for a new process relation called 2 3 - bisimulation —which lies strictly between that of simulation and bisimulation. Finally, the ultimately strength of the testing language is shown to identify a new process relation called probabilistic bisimulation—which is strictly stronger than bisimulation.

Testing real-time systems using UPPAAL

This chapter presents principles and techniques for modelbased black-box conformance testing of real-time systems using the Uppaal model-checking tool-suite. The basis for testing is given as a network of concurrent timed automata specified by the test engineer. Relativized input/output conformance serves as the notion of implementation correctness, essentially timed trace inclusion taking environment assumptions into account. Test cases can be generated offline and later executed, or they can be generated and executed online. For both approaches this chapter discusses how to specify test objectives, derive test sequences, apply these to the system under test, and assign a verdict.

Automated Test Generation from Timed Automata

Abstract Testing is the most dominant validation activity used by industry today, and there is an urgent need for improving its effectiveness, both with respect to the time and resources for test generation and execution, and obtained test coverage. We present a new technique for automatic generation of real-time black-box conformance tests for non-deterministic systems from a determinizable class of timed automata specifications with a dense time interpretation. In contrast to other attempts, our tests are generated using a coarse equivalence class partitioning of the specification. To analyze the specification, to synthesize the timed tests, and to guarantee coverage with respect to a coverage criterion, we use the efficient symbolic techniques recently developed for model checking of real-time systems. Application of our prototype tool to a realistic specification shows promising results in terms of both the test suite size, and the time and space used for test generation.

Testing real-time embedded software using UPPAAL-TRON: an industrial case study

UPPAAL-TRON is a new tool for model based online black-box conformance testing of real-time embedded systems specified as timed automata. In this paper we present our experiences in applying our tool and technique on an industrial case study. We conclude that the tool and technique is applicable to practical systems, and that it has promising error detection potential and execution performance.

Formal Methods and Testing

Model Based Testing with Labelled Transition Systems.- Model-Based Testing of Object-Oriented Reactive Systems with Spec Explorer.- Testing Real-Time Systems Using UPPAAL.- Coverage Criteria for State Based Specifications.- Testing in the Distributed Test Architecture.- Testing from X-Machine Specifications.- Testing Data Types Implementations from Algebraic Specifications.- From MC/DC to RC/DC: Formalization and Analysis of Control-Flow Testing Criteria.- Comparing the Effectiveness of Testing Techniques.- The Test Technology TTCN-3.- Testability Transformation - Program Transformation to Improve Testability.- Modelling the Effects of Combining Diverse Software Fault Detection Techniques.

Time-Optimal Real-Time Test Case Generation Using Uppaal

Testing is the primary software validation technique used by industry today, but remains ad hoc, error prone, and very expensive. A promising improvement is to automatically generate test cases from formal models of the system under test.

Compositional Verification of Probabilistic Processes

We introduce a simple calculus of probabilistic processes and we apply it as basis for an initial investigation of compositional verification for probabilistic processes. In particular we study the problem of decomposing logical specifications with respect to operators of the calculus. This study identifies a new probabilistic logic, which is needed in order to support decomposition. Complete axiomatizations are offered for both the calculus and the logic.

Bisimulation through probabilistic testing (preliminary report)

We propose a language for testing concurrent processes and examine its strength in terms of the processes that are distinguished by a test. By using probabilistic transition systems as the underlying semantic model, we show how a testing algorithm with a probability arbitrary close to 1 can distinguish processes that are not bisimulation equivalent. We also show a similar result (in a slightly stronger form) for a new process relation called 2/3-bisimulation — lying strictly between that of simulation and bisimulation. Finally, the ultimately strength of the testing language is shown to identify an even stronger process relation, called probabilistic bisimulation.

Formal Verification of a Power Controller Using the Real-Time Model Checker UPPAAL

A real-time system for power-down control in audio/video components is modeled and verified using the real-time model checker UPPAAL. The system is supposed to reside in an audio/video component and control (read from and write to) links to neighbor audio/video components such as TV, VCR and remote-control. In particular, the system is responsible for the powering up and down of the component in between the arrival of data, and in order to do so in a safe way without loss of data, it is essential that no link interrupts are lost. Hence, a component system is a multitasking system with hard real-time requirements, and we present techniques for modeling time consumption in such a multitasked, prioritized system. The work has been carried out in a collaboration between Aalborg University and the audio/video company B&O. By modeling the system, 3 design errors were identified and corrected, and the following verification confirmed the validity of the design but also revealed the necessity for an upper limit of the interrupt frequency. The resulting design has been implemented and it is going to be incorporated as part of a new product line.

An Evaluation Framework for Energy Aware Buildings using Statistical Model Checking

Cyber-physical systems are to be found in numerous applications throughout society. The principal barrier to develop trustworthy cyber-physical systems is the lack of expressive modelling and specification formalisms supported by efficient tools and methodologies. To overcome this barrier, we extend in this paper the modelling formalism of the tool UPPAAL-SMC to stochastic hybrid automata, thus providing the expressive power required for modelling complex cyber-physical systems. The application of Statistical Model Checking provides a highly scalable technique for analyzing performance properties of this formalisms.A particular kind of cyber-physical systems are Smart Grids which together with Intelligent, Energy Aware Buildings will play a major role in achieving an energy efficient society of the future. In this paper we present a framework in UPPAAL-SMC for energy aware buildings allowing to evaluate the performance of proposed control strategies in terms of their induced comfort and energy profiles under varying environmental settings (e.g. weather, user behavior etc.). To demonstrate the intended use and usefulness of our framework, we present an application to the Hybrid Systems Verification Benchmark.