The adaptive hypermedia systems or adaptive Web applications is a research area between hypermedia and user modeling. It can customize hyperspace to different users. The existing reference models are generic and are not dedicated to educational systems. This chapter presents in the first part a reference model that is specific to adaptive educational hypermedia systems. This model is called ALEM (Adaptive Learning Environment Model). It consists of a domain model, a learner model, a course structuring model and an adaptation model. The main contribution of this model is modeling the adaptive learning curriculum. Furthermore we develop the UML Tutor application which is an educational adaptive hypermedia system based on our reference model.