Infrastructure

S oftware-based systems today increasinglyoperate in changing environments withvariable user needs, resulting in the con-tinued increase in administrative overheadfor managing these systems. To reduce these costs, systems are increasingly expected to dynamically self-adapt to accommodate resource variability, changing user needs, and system faults. Mechanisms that support self-adaptation currently exist in the form of programming language features such as exceptions and in algorithms such as fault-tolerant protocols. But these mechanisms are often highly specific to the application and tightly bound to the code. As a result, self-adaptation in today’s systems is costly to build, difficult to mod-ify, and usually provides only localized treatment of system faults. In contrast to these internal mechanisms, recent work uses external models and mechanisms in