DOI: 10.1145/1178418.1178431Multiplayer online game (MOG) middleware is a set of software toolkits that assists and simplifies the MOG development process. Using the middleware enables developers to focus more resources on improving game design while spending less time and money on 3D rendering and server infrastructure issues. As the scale of MOGs grows rapidly, providing scalable data-sharing service, or interest management, becomes one of the major requirements for MOG middleware. In this article we present the details of the interest management system of our MOG middleware, Lucid Platform. We employ the data distribution management (DDM) service of the high-level architecture (HLA) as the main concept of our design. Since the message-filtering mechanisms of DDM are very complex and may impose significant computational overheads, we use an efficient interest-matching algorithm for the implementation. Experimental results, based on the demo games and the emulator programs, show that our approach works well in practice.