A Decentralized Adaptive Architecture for Ubiquitous Augmented Reality Systems
Asa MacWilliams · mediaTUM – the media and publications repository of the Technical University Munich (Technical University Munich) · 2005
Ubiquitous augmented reality is an emerging human-computer interaction technology, arising from the convergence of augmented reality and ubiquitous computing.Augmented reality allows interaction with virtual objects spatially registered in the user's real environment, in order to provide information, facilitate collaboration and control machines.As the computing and interaction devices necessary for augmented reality become ubiquitously available, opportunities arise for improved interaction and new applications.Building ubiquitous augmented reality systems presents three software engineering challenges.First, the system must cope with uncertainty regarding the software components; the users' mobility changes the availability of distributed devices.Second, during development, the system's desired behavior is ill-defined, as appropriate interaction metaphors are still being researched and users' preferences change.Third, the system must maintain near-real-time performance to create a convincing user experience.This dissertation presents a new architectural style, the adaptive service dependency architecture, to address these challenges.The architecture deals with component uncertainty, using middleware for decentralized service management to dynamically adapt the system's structure.It builds on existing architectural approaches, such as loosely coupled services, service discovery, reflection, and data flow architectures, but additionally considers the interdependencies between distributed services and uses them for system adaption.With the development technique of design at run time, users and developers address illdefined requirements by changing the system's behavior while it is running, facilitating the creation of new applications.This is based on existing agile development methods, but takes additional advantage of the architecture's adaptive and reflective properties.Distributed middleware maintains the required performance by decoupling multimedia data flow from system reconfiguration.It combines existing communication and service discovery technologies, but additionally deals with the distributed coordination of networks of interdependent services.Several prototype systems for real-world ubiquitous augmented reality applications have been built using the adaptive service dependency architecture, decentralized middleware, and design at run time.Feedback from users and developers, as well as performance tests, show the concepts' usefulness for building ubiquitous augmented reality systems. PrefaceIn the summer of 1999, I had the lucky opportunity to take part in a summer school, organized by the Technische Universität München, on the subject of augmented reality and wearable computers.Since then, I have been fascinated by the subject: a technology offering great potential, but also a multitude of research problems.As a result of this summer school, a group of enthusiastic students, including myself, determined to build a software framework for mobile augmented reality.We set out to combine what we could learn from our group's professors on the subjects of software engineering (Bernd Brügge) and augmented reality (Gudrun Klinker).The resulting framework was named DWARF, and in my Diplomarbeit, I reported on the middleware of its first prototype.The domain of ubiquitous augmented reality has proven challenging enough that several members of our group have continued to work in the area, and after four additional years, I am pleased to report the new results.I have been fortunate to receive the support of many people in completing this dissertation.