This monograph presents a comprehensive state-of-the-art survey on approaches to the design of intelligent agents. On the theoretical side, the author identifies a set of general requirements for autonomous interacting agents and provides an essential step towards understanding the principles of intelligent agents. On the practical side, the novel agent architecture InteRRaP is introduced: the detailed description and evaluation of this architecture is an ideal guideline and case study for software engineers or researchers faced with the task of building an agent system.The book uniquely bridges the gap between theory and practice; it addresses active and novice researchers as well as practitioners interested in applicable agent technology.