In [#!SchThWe1993!#] the environment dependent parameters are managed by dynamic environment servers . If an application is interested in the parameters of a dynamic environment server, it must subscribe to the server. For the communication between the application and the server RPC is used. The application can retrieve parameters from the server, but the server can also notify the application by callbacks about changes in the environment.
[#!No2000!#] presents a scenario, where a small personal digital assistant (PDA) guides tourists through a museum or a city delivering multimedia information about touristic attractions. The PDA must handle changing bandwidth and be aware about the tourist's location in order to present the interesting information of the location. The focus of [#!No2000!#] is to decide whether the adaptation is executed by the application, called laissez-faire application . If the adaptation is triggered by the operating system, the adaptation is called application-transparent system . The application has the knowledge, which amount of resources is necessary, whereas the operating system has an overview of the running applications and can manage the shared resources. The conclusion of [#!No2000!#] is a collaboration of operating system and application, denoted as application-aware collaboration . The collaboration is realized as an adaptive decision loop in the application. Inside the loop the application selects the data quality and requests the according resources. The application is informed by the operating system about changes of the resources. After notification the application selects a new data quality and redefines its resource requests.
A similar scenario is presented in [#!Abo1998!#]. The work presented in this section deals with different problems involved in manipulating parameters than dynamic adaptation which exchanges executable code. The common object of continuous adaptation and dynamic adaptation is the detection of the environment in order to determine the right adaptation. The information retrieval from the environment is based on application specific sensors, like active badges [#!WaHo1992!#], and not on generic properties of the hard- and software configuration, as targeted by this work.