With the advent of recent technological advances, more demanding tele-immersive applications have started to emerge. In the World Opera application, artists from different opera houses across the globe can participate in a single united performance, and interact almost as if they were co-located. One of the main design challenges in this application domain is to assess to what extent the inevitable failures of some of the numerous and complex hardware, software, and network components affect the quality of experience for the user. This challenge cannot be addressed by traditional system-centric methods for dependability evaluation, which do not take personalized user perspective into account when considering meaningful and acceptable degradation of services. In this paper, we propose a novel method to assess the quality of experience in presence of failures, based on a new metric called perceived reliability. The method takes the human perspective into account and allows considering factors such as human perception of video and audio, characteristics of the audience, as well as performance elements and artistic content. This method can help system designers and engineers compare architectural variants and determine the dependability budget. We show the feasibility of our method by applying it to a World Opera performance. To this end, we construct a SAN-based model and run simulations in the Möbius framework. The obtained results provide useful guidelines for system engineers towards improving the quality of experience of World Opera performances despite the presence of failures.

Analysis of interdependencies in Electric Power Systems (EPS) has been recognized as a crucial and challenging issue to improve their trustworthiness. The recent liberalization process in energy markets has promoted the entry of a variety of operators in the electricity industry. The resulting new organization contributed to increase in complexity, heterogeneity and interconnection. This paper proposes a framework for analyzing EPS organized as a set of interconnected regions, both from the point of view of the electric power grid and of the cyber control infrastructure. The emphasis is on interdependencies and in assessing their impact on indicators representative of the QoS perceived by users. Taking a reference power grid as test case, the effects of failures on selected measures are shown, both in case the grid is partitioned in a number of regions and in case of a single region, to illustrate the behavior of different grid and control configurations.