PrefaceOne the central themes of this book is the interplay between representation and behavior. Representation is about the way we look at our world, about how we see the things around us, and about how we think about and evaluate the concepts and knowledge that shape our surroundings.Behavior is about what we do, about our actions in the world or the mental actions in our head, and about the consequences of a wide variety of activities we engage in every day. Our representation of the world determines our behavior, but at the same time, our behavior influences what we see, and with that, it changes our representation of the world. This strange, mutually modifying loop is a fascinating phenomenon and it is the core object of study in both psychology and artificial intelligence. Indeed, much of the material in this book is about formal models and algorithms that characterize how computer-based, intelligent systems can represent their mathematical worlds and how they can behave rationally in such worlds. However, the pattern of this loop is much more general, and can be observed almost anywhere. For example, every paper I read changes my representation of my own scientific world, but at the same time, my research activities determine my choices for further study.Out of the many possible things that may be present in your representation of your world, and that may be part of your behavioral pattern, are people. Most of our representations of our world, our thinking, our talking, and our behavioral patterns, involve people. Especially in the path leading to this book, my representation of the world, and my course of action, have been influenced by so many people. For starters, in the writing of this book I have been influenced by many great scientists. There are many of them who I know personally and with whom I had the privilege to engage in interesting interactions, but there are many others that have influenced me without them knowing, for example when I attended their talks or read their books and papers. At this place, I want to express my gratitude to a number of specific people that have influenced me, helped me, supported me and made my life so much more interesting and enjoyable.First of all, I would like to thank my promotor Anton Nijholt for giving me the opportunity to do a PhD in his research group, and for the complete freedom and support he has given me to pursue my own interests, even when my path led me to new topics, to Utrecht and even to Freiburg. I thank Mannes Poel for all his support, his open-door policy that made it possible to just drop by with a coffee and start a discussion on any topic that was on my mind at those specific moments, for all the fun lunch walks, the stimulating educational activities we did together and all the other things that made our interactions fun and interesting.Many thanks go to my promotor John-Jules Meyer. His endless kindness, support and expertise have had great influence on my journey through my PhD period. I vividly remember our productive discussions, alwa...