Adaptation is often considered a complex issue during the design of a case-based reasoning system. Various approaches can be found in the literature, but their scopes are often limited to a relatively narrow range of applications. However, a general approach to adaptation based on belief revision has been developed over the years and applied in several formalisms, these formalisms being chosen for particular needs. This article presents the first version of Olaaaf, a general adaptation prototype based on belief revision whose long-term objective is to cover a wide range of adaptation processes. It is based on a formalism that covers both attribute-value pairs (often used for representing cases) and taxonomies (often used for representing domain knowledge). It is shown through an example how this system works, and it is discussed how it can be used for other complex adaptations.