Efficient Adaptation Decision Making Algorithms for Context-Aware Applications

2.1 Context

Context information is information that provides relevant knowledge about the environment of a system. Well know examples are the available memory resources or battery level of a mobile device, the user’s name, age and location or the light level in a room. Many definitions of context are given in related work, but the most frequently used is given by Dey (2001):

It follows that context information is very open for interpretation and is relative to the application needs. Chen and Kotz (2000) presented a classification of context information into three types: computing, environmental, and user context. Computing context describes the information about the infrastructure available to the system. Available memory or processing resources, type of network and battery level are common examples. Environmental context covers all the information about the physical environment of the system and its users. The location of a user and the noise or light level in a room are common examples. Finally user context describes the information about the users and their actions. The profile of a user, his mood and agenda are common examples. The sensing of and reasoning with context-information is extremely important for the realization of adaptive behavior. It allows the system to evaluate its fitness and the provided Quality of Service in the current environment. When, at a certain moment, this fitness becomes too low, an adaptation can be required.