Massively Multiplayer Online Games are becoming increasingly popular on the Internet. However, implementing them with a conventional Client/Server architecture suffers from various technical and commercial drawbacks. This has awakened research interest in adapting MMOGs to a Peer-to-Peer architecture. This paper surveys six essential issues in the implementation of a P2P MMOG. They are interest management, game event dissemination, NPC host allocation, game state persistency, cheating mitigation and incentive mechanisms.

Publish / subscribe is a well-known mechanism adopted by many applications to allow entities interested in certain information (i.e., the subscribers) to receive relevant messages from certain message generators (i.e., the publishers). We argue that for networked or distributed virtual environment (VE) applications, a spatial publish / subscribe (SPS), where each entity can receive messages generated within a specified space in the VE, is a fundamental mechanism underlying various VE applications. It is therefore of importance for the VE community to understand the main characteristics and limitations of SPS. This paper describes the basic mechanism of SPS, and how it can be used to support various existing VE requirements such as overlay management, state management, or content management. Potential ways to implement SPS are also outlined to allow interested parties to develop their own implementations.

When dealing with dynamic and large-scale topologies such as those underlying peer-to-peer (P2P) distributed virtual environments (DVE), one inescapably reaches the point where either real-life user input during simulations or experiments within test environments do not reach a critical mass to be considered strong and sustainable proof of the applied concepts. The restrictions resulting from the reciprocity and strict disjunction of simulation and test environments make it cumbersome to get a comprehensive assessment, and thus hinder more efficient development of adaptive algorithms and techniques for DVEs as they are investigated in our HyperVerse research project. Within this paper we present a hybrid evaluation system designed to combine the advantages of simulations and experiments. The proposed infrastructure exhibits great flexibility particularly alluring in view of the multitude of potential research in the context of DVEs.

This paper presents the design, implementation and evaluation of Deadline-Driven Auctions (DDA), a novel task mapping infrastructure for heterogeneous distributed environments. DDA is primarily designed to support the hosting of Non-Player Characters (NPCs) in P2P Massively Multiplayer Online Games (MMOGs). Experimental and analytical results demonstrate that DDA provides four significant advantages. Firstly, it is self-organising as the infrastructure can be automatically assembled and managed. Secondly, it efficiently allocates computing resources for large numbers of real-time NPC tasks in a simulated P2P MMOG with the better part of 1000 players. Thirdly, it supports gaming interactivity by keeping the communication latency among NPC hosts and ordinary players low. Finally, it supports flexible matchmaking policies, and with a friendly incentive policy, can establish a cooperative economic model that helps motivate application participants to contribute their resources to the system.

Massively Multiplayer Online Games and Virtual Worlds are among the most popular applications on the Internet. As player numbers increase, the limits of the currently dominant client/server architecture are becoming obvious. In this paper we propose a new distributed event dissemination protocol for Virtual Worlds and MMOGs. This protocol is based upon the idea of mutual notification: All players send their game event messages directly to all neighboring players inside their Area of Interest. The connectedness of the system is ensured by binding neighbors. They are selected using quad-trees. We show by simulation that the proposed system achieves practical performance for Virtual Worlds and Massively Multiplayer Online Games.

In this paper, we discuss interaction interoperability in Collaborative Virtual Environments (CVE), intended to mean the ability of two or more users to cooperate despite the heterogeneity of their interfaces. To allow such interoperability, rather than focusing on the de-coupling of input devices from interaction techniques and from interaction tasks, we suggest integrating interactive systems at higher level through an interface standardization. To achieve this aim, we propose: i) an architectural model able to handle differences in input devices and interaction tasks; ii) an agent-based middleware that provides basic components to integrate heterogeneous user interfaces. We also present a prototype of an agent-based middleware able to support developers in the interconnection of monolithic applications and we introduce tools and languages we have used to formalize the interaction tasks considered in the case study.