In modern Web-based information systems (WIS), the personalization of presentations and contents is becoming a major requirement. Personalization means adaptation to user’s requirements and goals, as well as adaptation to user’s technology and environment (Levene & Poulovassilis, 2004). Application fields where content personalization can be useful are manifold; they comprise e-government, online advertising, direct Web marketing, electronic commerce, online learning and teaching, and so forth. The need for adaptation arises from different aspects of the interaction between users and Web/hypermedia systems. User classes to be dealt with are increasingly heterogeneous due to different interests and goals, large-scale deployment of information and services, and so on. Furthermore, WIS should be made accessible from different user’s terminals, which can differ not only at the software level (browsing and elaboration capabilities) but also in terms of ergonomic interfaces (scroll buttons, voice commands, etc.). Finally, different kinds of network (e.g., wired or wireless) and other network-related conditions (e.g., bandwidth, latency, error rate, etc.) should be considered to obtain a comfortable and useful interaction.