Adaptive Educational Hypermedia Systems have the potential to deliver instruction tailored to the characteristics of each student. However, despite many years of research in the area, these systems have been used only in a few real learning situations. Reasons for this include their use of proprietary semantics in the definition of adaptivity and educational elements, and their lack of interoperation among courses and applications. We claim that an option to overcome these issues is to annotate adaptive rules, techniques, and learning elements using a common notational method, the IMS Learning Design (IMS LD). This paper presents a novel approach to define adaptive learning designs and, particularly, how adaptive hypermedia techniques and adaptive rules can be modelled by means of IMS LD.