A framework for dependable adaptation in probabilistic environments

Distributed applications executing in probabilistic environments, like the Internet, often need to make timing assumptions, for instance about the maximum message delay or the round-trip delay. In the case of adaptive systems these bounds should be computed at run-time, using probabilistic or other more or less ad hoc approaches, typically with the objective of improving the application performance. From a dependability perspective, however, the concern is to secure some properties on which the application can rely. Building on previous work where we set the stage for dependable adaptation, we introduce a general framework for implementing improved solutions for dependable adaptation. During its lifetime, a system alternates periods where its temporal behavior is well characterized, with transition periods where a variation of the environment conditions occurs. The proposed framework rests on the detection of these stable and transient phases, and it is generic in the sense that different detection mechanisms can be included. We use a set of simple phase detection mechanisms inspired in well-known probabilistic tests, along with synthetically generated data flows, to illustrate how the framework can be applie

Revised reference model

This document contains an update of the HIDENETS Reference Model, whose preliminary version was introduced in D1.1. The Reference Model contains the overall approach to development and assessment of end-to-end resilience solutions. As such, it presents a framework, which due to its abstraction level is not only restricted to the HIDENETS car-to-car and car-to-infrastructure applications and use-cases. Starting from a condensed summary of the used dependability terminology, the network architecture containing the ad hoc and infrastructure domain and the definition of the main networking elements together with the software architecture of the mobile nodes is presented. The concept of architectural hybridization and its inclusion in HIDENETS-like dependability solutions is described subsequently. A set of communication and middleware level services following the architecture hybridization concept and motivated by the dependability and resilience challenges raised by HIDENETS-like scenarios is then described. Besides architecture solutions, the reference model addresses the assessment of dependability solutions in HIDENETS-like scenarios using quantitative evaluations, realized by a combination of top-down and bottom-up modelling, as well as verification via test scenarios. In order to allow for fault prevention in the software development phase of HIDENETS-like applications, generic UML-based modelling approaches with focus on dependability related aspects are described. The HIDENETS reference model provides the framework in which the detailed solution in the HIDENETS project are being developed, while at the same time facilitating the same task for non-vehicular scenarios and application