For the protection of large sites with high values that are continously threatened by attacks and accidents, complex sensing and decision systems are necessary for an efficient protection. Examples for such sites are airports, harbours, railway stations, power plants, critical research facilities and all public areas. Based on the data from many different sensors, like video cameras, microphones, mechanical, chemical sensors and many others, information about the actual situation must be delivered by means of automatic and interactive evaluation. For the realisation of systems for this purpose, a general applicable architecture for the construction shall be defined. The organisation of devices, services and applications will be organised in a web based service oriented architecture. For the operation, interaction, decision and handling, three application layers are defined. The first is the top level decision layer, the second is the guidance layer and the third the fields operation layer. In each layers, systems for visualisation, interaction and simulation are required. For the top level decisions, the complete information has to be condensed in order derive the best solution for an adequate reaction. In addition to tasks matching services, ergonomic optimised interaction devices are required.