This book introduces major agent platforms, frameworks, systems, tools, and applications. Each system is described by their developers in sufficient detail so that the reader can get a good understanding of the architecture, functionality, and application areas of the system. All systems are running systems. One main focus of the book lies on agent platforms and toolkits. They form the basis for the development of agent-based systems, thus, are a convenient starting point for everybody who wants to apply agent technology. Another focus lies on agent-based applications. These systems prove that agent technology is mature enough to permit the development of sophisticated applications, like electronic marketplaces, environments for computer-supported cooperative work, or transportation systems.