Adaptation/personalization is one of the main issues for web ser-vices. Adaptive web applications have the ability to deal with different users?needs for enhancing usability and comprehension and for dealing with large repositories. We propose an open-ended adaptive hypermedia environment which is based on the virtual document and semantic web approaches and which is able to manage adaptive techniques at knowledge level. In this paper, we have focused on the way to specify and to manage adaptation in this environment. We propose an approach which is based on a unique evaluation principle of links/contents per document and where the author may assign user stereotypes to adaptive techniques.