In this dissertation I present a software framework for adaptable Augmented Reality systems in intelligent environments: the Distributed Wearable Augmented Reality Framework (DWARF). The framework is a reusable basis for the development of Augmented Reality applications and gives developers a system structure to customize existing or develop new components. Augmented Reality is a human-computer interaction paradigm offering users new possibilities to interact with their environment. By tracking the position and viewing direction of the user and of real world objects in the environment, real world objects can be augmented with virtual objects. The most prominent example is the overlay of real world objects with computer graphics in a head-mounted display. DWARF models Augmented Reality applications in four abstraction layers: application layer, inter-application layer, solution domain layer, and architectural style layer. For the architectural style layer, I specify a contract-based peer-to-peer style. A system is a configuration of mutually interdependent distributed services. The connections between services are established by an active middleware based on an abstract service specification. Existing solutions for Augmented Reality are usually designed as monolithic or client/ server systems. DWARF uses an extension of component-oriented software engineering. Components on the users computer and in the environment are both used as building blocks for Augmented Reality systems. Further on, I extend the component-based system approach to a service-based approach. An application is not built from instances of components, but from a configuration of services available on the users computer and in the environment. An active middleware enables the dynamic adaptation of the system to changes in the environment by a reconfiguration of the system. For the solution domain layer, I present an abstract reference architecture and a system of patterns for Augmented Reality systems. The foundation for them is a broad analysis of existing Augmented Reality systems. Finally, as a case study for the applicability of the framework, I present the subframework M3ARF for mobile maintenance systems and a navigation application as part of such a mobile Augmented Reality maintenance system, DWARF Pathfinder. This case study covers the application layer, the inter-application layer, and the solution domain layer.
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