1 Introduction
Distributed Interactive Applications (DIAs) are emerging technologies that open up new opportunities for geographically distributed participants to interact with each other via computer networks. Examples of DIAs include networked gaming [1], [2], distributed e-learning [3], and collaborative computer-aided design and engineering [4]. DIAs usually operate with client-server architectures [5] in which the servers maintain the application states, and execute the operations submitted by the participants who are known as clients. Owing to different ways of maintaining the application states, DIAs can be classified into two categories: discrete DIAs and continuous DIAs [6]. In discrete DIAs, the application states are only updated due to the operations performed by clients. In continuous DIAs, the application states not only change because of executing the client-initiated operations, but also evolve along with the elapse of time. A typical example of continuous DIAs is networked gaming, where the states of virtual game worlds are often updated at a fast pace even when there is no operation input from the players.