The problem of data persistency in distributed real-time interactive applications

The class of distributed Real-time Online Interactive Applications (ROIA) includes such important applications as Massively Multiplayer Online Games (MMOGs), as well as interactive e-Learning and simulation systems. These applications usually work in a persistent environment (also called world) which continues to exist and evolve also while the user is offline and away from the application. The challenge is how to efficiently make the world and the player characters persistent in the system over time. In this paper, we deal with storing persistent data of real-time interactive applications in modern relational databases. We analyze the major requirements on a system for persistency and we describe a preliminary design of the Entity Persistence Module (EPM) middleware which liberates the application developer from writing and maintaining complex and error-prone code for persistent data management. EPM automatically performs the mapping operations to store/retrieve the complex data to/from different types of relational databases, supports the management of persistent data in memory, and integrates it into the main loop of the ROIA client-server architecture.