Distributed Interactive Multimedia Applications (DIMA) are "human in the loop" applications. Their aim is to support real-world like interactions through a virtual world in a broader sense. However, propagation delays, jitter and losses due to network communications naturally lead to inconsistencies, when local and remote actions performed by users/clients are played out. This constraint makes the management of replicated multimedia shared data a real challenge. In the literature, various consistency models are proposed and each of them brings their own complexity and distortion among interactions. In this paper, we provide hints to help DIMA designers to choose appropriate consistency models by first presenting meaningful psycho-perceptive characteristics of the real-world interactions and then discussing various consistency models according to them.

We developed the Open Orchestra system to provide individual musicians with a high-fidelity experience of ensemble rehearsal or performance, combined with the convenience and flexibility of solo study. This builds on the theme of an immersive orchestral simulator that also supports the pedagogical objective of instructor feedback on individual recordings, as needed to improve one's performance. Unlike previous systems intended for musical rehearsal, Open Orchestra attempts to offer both an auditory and a visual representation of the rest of the orchestra, spatially rendered from the perspective of the practicing musician. We review the objectives and architecture of our system, describe the functions of our digital music stand, discuss the challenges of generating the media content needed for this system, and describe provisions for offering feedback during rehearsal.

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Ubiquitous computing architectures enable interaction and collaboration in multiuser applications. We explore the challenges of integrating the disparate services required in such architectures and describe how we have met these challenges in the context of a real-world application that operates on heterogeneous hardware and run-time environments. As a compelling example, we consider the role of ubiquitous computing to support the needs of a distributed multiuser game, including mobility, mutual awareness, and geo-localization. The game presented here, "SoundPark", is played in a mixed-reality environment, in which the physical space is augmented with computer-generated audio and graphical content, and the players communicate frequently over a low-latency audio channel. Our experience designing and developing the game motivates significant discussion related to issues of general relevance to ubiquitous game architectures, including integration of heterogeneous components, monitoring, remote control and scalability.