The formulation of queries is often regarded as a difficult task for a large class of users. In this article we propose an approach facilitating query formulation for users sharing a common database. Our approach is based on two considerations. On one hand, query formulation can be considered as a skill which can be shared entirely or partly between users. Accordingly we propose a model for storing and making available this skill to help users to formulate their new queries. On the other hand, we base our design on custom construction of a database adapted to each business group of users in question. In using it, the users of a given business cooperate transparently through their queries to design databases specific to their business. Thus, they take part co-operatively, if indirectly in reducing the difficulty of query formulation.