An OLAP analysis can be defined as an interactive session during which an user launches queries over a data warehouse. The launched queries are often interdependent, and they can be either newly defined queries or they can be existing ones that are browsed and reused. Moreover, in a collaborative environment, queries may be shared among users. This notion of OLAP analysis has never been formally defined. In this paper, we propose a clear definition of this notion, by introducing a model for sharing, browsing and reusing OLAP queries over a data warehouse.