The topic of this dissertation is the observation of physical world events through a distributed world model. So the events of interest occur in the world we live in. The basis for their observation is a model of the relevant aspects of the physical world. These include more static aspects like geometric models of stationary objects, e.g., houses and streets, but also dynamic aspects, e.g., the position of mobile users or the temperature.
With the proliferation of mobile computing devices like personal digital assistants or mobile phones with significant computing and communication capabilities, there is a trend to extend computer support from the desktop to the physical world. As the focus of the mobile user may be on other tasks, computer support should be proactive, providing the user with information and services relevant in his current situation. The observation of high-level physical world events is an enabler for these new kinds of services.
Due to the size of the data, different characteristics of the data, and a multitude of providers, the world model data needed for the observation can be distributed over a number of servers. We present a novel event service architecture that allows the observation of complex high-level events through a distributed world model.
As the accuracy of the data is limited due to the characteristics of both the underlying sensor data and the computer network, this has to be taken into account. We propose a concept for specifying physical world events together with a threshold probability above which the event is considered to have occurred. We then show how physical world events can be observed, calculating the occurrence probability and comparing this to the specified threshold probability.
Finally, we present an evaluation based on a prototype implementation with a number of concrete events. The focus of the evaluation is on both the performance and the quality of the observation, showing the general feasibility of our approach.
event, event service, event observation, world model, distributed system