Stuttgart, Univ., Diplomarb., 2002.

Stuttgart, Univ., Studienarb., 2001.

Stuttgart, Univ., Studienarb., 2001.

Zugl.: Diplomarbeit / Hergestellt on demand

Stuttgart, Univ., Diplomarb., 2002.

With the increasing ubiquity of smartphones, tablets, and large pixel-rich displays, there are many exciting new possibilities for using these devices for collaborative work. While there already exist hardware and software that support communication and interaction between mobile devices and shared displays, application sharing in these scenarios is still limited and inflexible. We present a new method of application sharing which allows collaborators to download clips or snapshots of each other's applications. These snapshots can be used to re-launch and resume the shared application back to the state it was in when it was shared. We have built a system that supports sharing, annotating, organizing, and downloading these applications to and from a LearnSpace server. We have built an application framework which allows Android applications to be built for this system while only requiring minimal changes to the program. We also describe solutions for extending our solution to new types of collaborative displays and to other application platforms.

This dissertation analyzes the usefulness of existing "conventional" <b>collaboration-transparency</b> systems, which permit the shared use of legacy, single-user applications. I find that conventional collaboration-transparency systems do not use network resources efficiently, and they impose an inflexible, tightly coupled style of collaboration because they do not adequately support important groupware principles: concurrent work, relaxed WYSIWIS, group awareness, and inherently collaborative tasks. This dissertation proposes and explores solutions to those deficiencies. The primary goal of this work is to maintain the benefits of collaboration transparency while relieving some of its disadvantages. To that end, I present an alternate implementation approach that provides many features previously seen only in applications specifically designed to support cooperative work, called <b>collaboration-aware</b> applications. The new approach uses a replicated architecture, in which a copy of the application resides on each user's machine, and the users' input events are broadcast to each copy. I discuss solutions to certain key problems in replicated architectures, such as maintaining consistency, unanticipated sharing, supporting late-joiners, and replicating system resources (e.g., files, sockets, and random number generators). To enhance the collaborative usability of a legacy application, the new approach <i> transparently</i> replaces selected single-user interface objects with multi-user versions at runtime. There are four requirements of an application platform needed to implement this approach: process migration, run-time object replacement, dynamic binding, and the ability to intercept and introduce low-level user input events. As an instance of this approach, I describe its incorporation into a new Java-based collaboration-transparency system, called Flexible JAMM (Java Applets Made Multi-user). This dissertation reports the results of a controlled empirical study that evaluated the usefulness of Flexible JAMM versus a representative conventional collaboration-transparency system, Microsoft NetMeeting. The results validate that Flexible JAMM meets its goals, and uncover usability problems in both systems, particularly with respect to using floor control. Additionally, the dissertation reports the results of an informal study that evaluated using Flexible JAMM as a groupware toolkit. This dissertation demonstrates that it is possible to bring collaboration transparency closer to the advantages afforded by collaboration awareness. Furthermore, the prototype system demonstrates that collaboration-aware toolkits can include multi-user versions of some standard single-user components that require no collaboration-specific programming by the toolkit user. Thus, the results of this research advance the state of the art in both collaboration-transparency systems and collaboration-aware toolkits. / Ph. D.