The 7 full papers presented together with 6 invited papers were carefully selected for inclusion in the book. The authors' revisions have been significantly improved by the reviewers' comments and the discussions following the presentation at the workshop. The papers are organized in topical sections on overall design and fundations, algorithms and techniques, applications, as well as self-organization and evolutionary computing.

The Fourth International Workshop on Engineering Self-Organizing Applications (ESOA) was held on May 9, 2006 in conjunction with the 2006 Conference on Autonomous Agents and Multi-Agent Systems (AAMAS 2006), in Hakodate, Japan. The present post-proceedings volume contains revised versions of the seven papers presented at the workshop, and six additional invited papers. Continuing the tradition of previous editions, this book discusses a broad variety of topics in an effort to allow room for new ideas and discussion, and eventually a better understanding of the important directions and techniques of our field.

In “Hybrid Multi-Agent Systems: Integrating Swarming and BDI Agents”— an article based on an invited talk at the workshop by Van Parunak—Parunak et al. address an important question facing the ESOA community: how should self-organizing swarm-like agent approaches relate to the techniques of the multiagent community at large? ESOA techniques primarily rely on simple reactive agents, whose intelligence emerges at the group level via carefully designed interaction rules. These simple agents might have some internal state that allows them to remember the history of their interactions at some (low) level of detail, but generally the complexity in such systems arises from the dynamics. In contrast, the mainstream multi-agent systems community uses intelligent agents, which apply sophisticated algorithms to build up internal models of their environments and complex protocols to communicate about their models. This general approach, of which the BDI frameworks are an example, warrant a more cognitive analogy than the typical ESOA ideas. Parunak et al.’s work shows how the two approaches could profitably interact.