CASA – A Contract-based Adaptive Software Architecture Framework∗

Traditionally, applications are developed with an implicit reliance on the stability of their execution environment and available resources, while little or no support is provided for the runtime adaptation of application behavior in case of any instability encountered. But such an approach proves futile for more dynamic environments, such as those encountered in self-organized mobile networks, wherein any form of reliance on the runtime computing environment of an application would be highly optimistic. The Contract-based Adaptive Software Architecture (CASA) framework, described in this paper, addresses the need to equip an application with the ability to dynamically adapt itself in response to changes in its execution environment. This implies that an application is able to meet its functional and/or non-functional commitments even when its runtime computing environment changes. The framework builds on the idea of specifying resource requirements and adaptation behavior of applications in application contracts.