Web information systems are a cornerstone of IT architectures at the present time. In particular, they are used as knowledge management portals, intranets and "Wikis," which are intended to satisfy information needs of users or customers as efficiently as possible. However, due to a vast amount of information as well as "fuzzy" problem situations, information seeking becomes increasingly difficult, time-consuming and costly . The development of web information systems is neither a purely technical nor a merely conceptual problem. Both aspects have to be taken into consideration simultaneously in order to facilitate the development of efficient web information systems. Conceptual modelling of navigation structures can be used as a tool to specify, explicate and discuss the linguistic means available for users to locate relevant pieces of information in vast information spaces. Christian Stephan Brelage discusses the problem of human information processing in the context of web information systems. He proposes a modelling approach as well as a conceptualization with special regard to the design of navigation structures. Both can be used to facilitate and improve the development of web information systems in theory and practice. This book is directed at practitioners and academics in the fields of information systems, information system development, conceptual modelling and web information systems. Christian Stephan Brelage studied Information Systems at the University of M"unster and the University of Alabama, Tuscaloosa. He worked as a Research Assistant at the European European Research Center for Information Systems (ERCIS). His reserarch concentrates on web information systems, conceptual modelling and information system development. He received his PhD degree in information systems in November 2005.