This book describes new knowledge-based approaches for developing complex, next-generation electronic services and web-based applications. It comprises several examples of how we can deal with the challenges that typically increase the complexity of the development of such systems, such as the need for personalized user interfaces, the debugging problem for knowledge-based systems, or the challenges of developing systems consisting of co-operating electronic Web services. For researchers and students, the book shows how these current advances in Artificial Intelligence techniques and Knowledge-Based systems can help us to implement intelligent behavior in tomorrow's web-based applications more easily. For the practitioner, the real-world applications and practical examples described in the book also demonstrate that such novel techniques are already mature enough to be incorporated into the technical environment of today's web applications.