We present a new formal approach to retrieval personaliza- tion which emcompasses a query personalization process at the user's side with a light document adaptation at the in- formation server's side. Our solution relies on the use of a domain ontology: queries and documents are in fact indexed by sets of concepts. For each concept of the query, the query personalization process allows to express the importance of linked concepts, which may vary according to the search con- text. Each query concept can be ”clarified” by this process; although the proposed method clarifies only central query concepts. The initial query as well as its defined clarifica- tions are sent to the server. Then, the server reconsiders its document representations based on both the query and the concepts clarifications it received. The proposed solution does not require that the information server maintains any user profile, and can be useful when, for privacy concerns, it is committed not to profiling the users.