The performance and dependability of critical infrastructures, such as water-treatment facilities is essential. In this paper we use various performance and dependability measures to analyze a simplified model of a water treatment facility. Building on the existing architectural framework Arcade a model is derived in XML format and then automatically mapped to the model checker PRISM. Using the stochastic model checking capabilities that PRISM offers, we compare different repair strategies, with respect to their costs, system reliability, availability and survivability. For this case study we conclude that using non-preemtive priority scheduling with additional repair crews is the best choice with respect to performance, dependability and costs.

This paper proposes a formally well-rooted and extensible framework for dependability evaluation: Arcade (architectural dependability evaluation). It has been designed to combine the strengths of previous approaches to the evaluation of dependability. A key feature is its formal semantics in terms of input/output-interactive Markov chains, which enables both compositional modeling and compositional state space generation and reduction. The latter enables great computational reductions for many models. The Arcade approach is extensible, hence adaptable to new circumstances or application areas. The paper introduces the new modeling approach, discusses its formal semantics and illustrates its use with two case studies.

This paper discusses the requirements that a suitable formalism for dependability modeling/evaluation should possess. We also discuss the outline of Arcade, an architectural dependability formalism that we are developing.

Recent results on GaAs-based high-speed mode-locked quantum-dot (QD) lasers and optical amplifiers with an operation wavelength centered at 1290 nm are reviewed and their complex dependence on device and operating parameters is discussed on the basis of experimental data obtained with integrated fiber-based QD device modules. Hybrid and passive mode locking of QD lasers with repetition frequencies between 5 and 80 GHz, sub-ps pulse widths, ultralow timing jitter down to 190 fs, high output peak power beyond 1 W, and suppression of Q-switching are reported, showing the large potential of this class of devices for O-band optical fiber applications. Results on cw and dynamical characterization of QD semiconductor optical amplifiers (SOAs) are presented. QD amplifiers exhibit a close-to-ideal noise figure of 4 dB and demonstrate multiwavelength amplification of three coarse wavelength division multiplexing (CWDM) wavelengths simultaneously. Modelling of QD polarization dependence shows that it should be possible to achieve polarization insensitive SOAs using vertically coupled QD stacks. Amplification of ultrafast 80 GHz optical combs and bit-error-free data signal amplification at 40 Gb/s with QD SOAs show the potential for their application in future 100 Gb Ethernet networks.

In the past, logics of several kinds have been proposed for reasoning about discrete-time or continuous-time Markov chains. Most of these logics rely on either state labels (atomic propositions) or on transition labels (actions). However, in several applications it is useful to reason about both state properties and action sequences. For this purpose, we introduce the logic as CSL which provides a powerful means to characterize execution paths of Markov chains with actions and state labels. asCSL can be regarded as an extension of the purely state-based logic CSL (continuous stochastic logic). In asCSL, path properties are characterized by regular expressions over actions and state formulas. Thus, the truth value of path formulas depends not only on the available actions in a given time interval, but also on the validity of certain state formulas in intermediate states. We compare the expressive power of CSL and asCSL and show that even the state-based fragment of asCSL is strictly more expressive than CSL if time intervals starting at zero are employed. Using an automaton-based technique, an asCSL formula and a Markov chain with actions and state labels are combined into a product Markov chain. For time intervals starting at zero, we establish a reduction of the model checking problem for asCSL to CSL model checking on this product Markov chain. The usefulness of our approach is illustrated with an elaborate model of a scalable cellular communication system, for which several properties are formalized by means of asCSL formulas and checked using the new procedure

In this paper we introduce the logic asCSL, an extension of continuous stochastic logic (CSL), which provides powerful means to characterise execution paths of action- and state-labelled Markov chains. In asCSL, path properties are characterised by regular expressions over actions and state-formulas. Thus, the executability of a path not only depends on the available actions but also on the validity of certain state formulas in intermediate states. Our main result is that the model checking problem for asCSL can be reduced to CSL model checking on a modified Markov chain, which is obtained through a product automaton construction. We provide a case study of a scalable cellular phone system which shows how the logic asCSL and the model checking procedure can be applied in practice.