Personalisation systems provide individualised services. Their usefulness and success depend on the accuracy of their knowledge about their respective users. In this context, user modelling refers to the acquisition, creation, storage, maintenance, and delivery of knowledge about users. Further, a personalisation system can also benefit from additional internal models of other entities in its environment, such as communication devices or specific sensors. This additional knowledge increases its capability of adapting successfully for different purposes. The need for the application of such systems can be currently found in areas including e-learning, e-commerce, recommender systems, and ubiquitous computing. This book presents research and development towards a Multi-purpose Modelling System. The result is a flexible and reusable software framework for modelling users of adaptive systems.