Sensor networks as well as radio frequency identification (RFID) systems are among the hyped technologies nowadays. A lot of research efforts have been spent to develop standards, middleware and applications. The industry has already made large investments to foster the adoption of these technologies, consequently pushing the development, and already deploying the resulting technologies in different domains. However, the addressed technologies are still very young; best practices as well as standards are expected to frequently change, as new demands arise when using the technologies in everyday life. Because of this, middleware systems are expected to undergo frequent redesigns as well, requiring well-suited design paradigms to avoid a software engineering nightmare. We therefore propose an agent-based middleware for sensor networks and RFID systems. This middleware will meet the challenges for having a robust, adaptable and flexible middleware, which is, moreover, easily extensible to cope with expected re-engineerings and changes while maintaining a clear and elaborate design.