Virtual worlds use simulation to create a fully-immersive 3D space in which users interact and collaborate in real time. It is still a great challenge to scale virtual worlds to provide rich user experiences, high level of realism, and innovative usages. There are three unique simulation requirements in scaling virtual worlds: (1) large-scale, real time and perpetual simulations with distributed interaction, (2) simultaneous visualization for many endpoints with unique perspectives, and (3) multiple simulation engines with different operation characteristics. In this paper, we review the challenges in meeting these requirements, present the scalability barriers we observed in current virtual worlds, and discuss potential virtual world architecture and solutions to address the challenges and overcome the barriers. INTRODUCTIONVirtual worlds use simulation to create a fully-immersive 3D space for users to explore, collaborate, and interact in real time. There are two broad classes of popular virtual worlds: general purpose virtual worlds, such as Second Life®, and massively multiplayer online games, such as World of Warcraft™. Scalability, however, is still a great challenge in virtual worlds. For instance, Second Life and World of Warcraft are limited to below 100 users interacting with each other concurrently (Gupta et al. 2009). To meet the increasing demand of rich user experiences, high level of realism, and new usages such as experiencing professional sports games in virtual auditoriums, virtual worlds must scale beyond their current capability in several dimensions.The first dimension is to scale the number of concurrent users interacting with each other. Current virtual worlds have to split the user base and restrict interactions to achieve scalability. For instance, Second Life applies static space partitioning to decompose the space into 256m x 256m regions, each handled by one server. World of Warcraft uses sharding: a part of the virtual world is replicated into shards and different shards reside on different servers, but users on different shards are isolated from each other. Both approaches degrade the massive multi-user experience: sharding prevents large groups of users from interacting by design and static partitioned regions collapse with too many users (Gupta et al. 2009).The second dimension is to scale the scene complexity, captured by the number of objects and the complexity of their behaviors and appearance. It is especially challenging in general purpose virtual worlds, where user generated content is dominant. Designers of such a world only provide tools, basic parts, and primitive objects (prims) to enable users to be creative and produce content. There is no limitation on what users can build and potentially infinite set of object behaviors could be expressed, hence the term "general purpose". As such, the tools and prims are not optimized for any special purposes. When a 778 978-1-4244-9865-9/10/$26.00 ©2010 IEEE

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Automatic service and application deployment and management is becoming possible through the use of service and infrastructure discovery and policy systems. But using the infrastructure optimally requires intimate knowledge of the hardware and the interaction of its components in order to make optimal allocation of shared resources. This paper proposes an architecture where the hardware infrastructure not only makes operational parameters available (disk size, network bandwidth) but also presents to the service management components, relationships and constraints between the hardware components. We present an implementation which uses the Service Modeling Language, SML, to communicate this information and show how this architecture saves service management from knowing intimate knowledge of the hardware. This enhances optimal service deployment and management in a heterogeneous hardware environment and is a step toward autonomic computing.Keywords-model based management; Service Modeling Language (SML); hardware/software management integration1

The Multimedia Interface for the Disabled (MIND) project is concerned with developing a set of guidelines and authoring tools, for use by multimedia developers, to enable them to augment their products to encompass the specific needs of sensory impaired users. This paper presents the ethos behind the project and describes the MIND software prototype developed. The MIND prototype maximises the effectiveness of multimedia information delivery, through the provision of an adaptable and easily navigated user interface, which incorporates access to the augmented multimedia information created with the authoring tools.