1 Introduction
Information systems attached to various types of heterogeneous data sources, which mainly consist of multiple sensors are required in many different applications that will be integrated into command and control systems. Applications can be both of military and civilian type and example of the latter may be emergency management where functionality for information fusion, i.e. basically for situation and impact assessments, are required. From a user's perspective this kind of systems will become very complex and consequently tools to control the sensor environment and, in the end, to support decision-making will be needed as well. These aspects can, however, be viewed as two sides of the same coin where the decision support tool is facing the end-user while the means for controlling the internal environment must be integrated into the system to control all aspects of the management of the sensors and the sensor data. In the latter case a controversy is apparent in that the question will arise whether the end-users of a multi-sensor system should be able to directly view the sensor data or whether they should just be able to overlook abstract high-level information extracted by the system in the query process. A solution to this problem is a system design characterized by the latter aspect, i.e. a system where the sensor raw-data will be hidden from the user.