Uli Fahrenberg

A Robust Specification Theory for Modal Event-Clock Automata

In a series of recent work, we have introduced a general framework for quantitative reasoning in specification theories. The contribution of this paper is to show how this framework can be applied to yield a robust specification theory for timed specifications.

Model Checking Real-Time Systems

This chapter surveys timed automata as a formalism for model checking real-time systems. We begin with introducing the model, as an extension of finite-state automata with real-valued variables for measuring time. We then present the main model-checking results in this framework, and give a hint about some recent extensions (namely weighted timed automata and timed games).

A Linear-Time–Branching-Time Spectrum of Behavioral Specification Theories

We propose behavioral specification theories for most equivalences in the linear-time–branching-time spectrum. Almost all previous work on specification theories focuses on bisimilarity, but there is a clear interest in specification theories for other preorders and equivalences. We show that specification theories for preorders cannot exist and develop a general scheme which allows us to define behavioral specification theories, based on disjunctive modal transition systems, for most equivalences in the linear-time–branching-time spectrum.

Trace checking for dynamic software product lines

A key objective of self-adaptive systems is to continue to provide optimal quality of service when the environment changes. A dynamic software product line (DSPL) can benefit from knowing how its various product variants would have performed (in terms of quality of service) with respect to the recent history of inputs. We propose a family-based analysis that simulates all the product variants of a DSPL simultaneously, at runtime, on recent environmental inputs to obtain an estimate of the quality of service that each one of the product variants would have had, provided it had been executing. We assessed the efficiency of our DSPL analysis compared to the efficiency of analyzing each product individually on three case studies. We obtained mixed results due to the explosion of quality-of-service values for the product variants of a DSPL. After introducing a simple data abstraction on the values of quality-of-service variables, our DSPL analysis is between 1.4 and 7.7 times faster than analyzing the products one at a time.

Optimal and Robust Controller Synthesis Using Energy Timed Automata with Uncertainty

In this paper, we propose a novel framework for the synthesis of robust and optimal energy-aware controllers. The framework is based on energy timed automata, allowing for easy expression of timing constraints and variable energy rates. We prove decidability of the energy-constrained infinite-run problem in settings with both certainty and uncertainty of the energy rates. We also consider the optimization problem of identifying the minimal upper bound that will permit existence of energy-constrained infinite runs. Our algorithms are based on quantifier elimination for linear real arithmetic. Using Mathematica and Mjollnir, we illustrate our framework through a real industrial example of a hydraulic oil pump. Compared with previous approaches our method is completely automated and provides improved results.

Higher-Dimensional Timed Automata

We introduce a new formalism of higher-dimensional timed automata, based on van Glabbeeks higher-dimensional automata and Alurs timed automata. We prove that their reachability is PSPACE-complete and can be decided using zone-based algorithms. We also show how to use tensor products to combat state-space explosion and how to extend the setting to higher-dimensional hybrid automata.

Compatibility flooding: measuring interaction of services interfaces

This paper proves the convergence of a compatibility flooding algorithm which measures the compatibility degree of service interfaces. This measuring method is generic and automated by a prototype tool.