The design and functioning of an information system improve to the extent that the system can handle the questions people ask. Surprisingly, however, researchers in the cognitive, computer, and information sciences have not thoroughly examined the multitude of relationships between information systems and questions -- both question asking and answering. The purpose of this book is to explicitly examine these relationships. Chapter contributors believe that questions play a central role in the analysis, design, and use of different kinds of natural or artificial information systems such as human cognition, social interaction, communication networks, and intelligent tutoring systems. Their efforts show that data structures and representations need to be organized around the questioning mechanisms in order to achieve a quick retrieval of relevant useful information.