Using spatial conditions for proactive computing and interaction metaphors

The position of a user with respect to devices or the relative position of multiple devices provides an indication of interaction that is intended by the user. Based on this assumption many applications proactively trigger an action when certain spatial conditions are fulfilled. A typical example is executing a local service when the proximity of a user is detected. This paper presents a concept of spatial conditions which aims to unitize the handling of such mechanisms. The concept is integrated in a toolkit that supports applications in making use of it. Furthermore we propose a new interaction technique for mobile devices, which is based on spatial conditions but at the same time avoids the disturbance of users by triggering unwanted services.