Nowadays, software engineers face a wide range of particular application domains such as electronic commerce, enterprise resource planning, mobile computing, self-organisation, pervasive and adaptive computing, etc. The resulting heterogeneity and required functionalities call for complex systems and open architectures that may evolve dynamically over time so as to accommodate new components and meet new requirements. This is probably one of the main reasons why the agent metaphor and agent-based computing are gaining momentum in these areas.