Rapid environmental changes require decentralized structures to ensure reactivity. In this context, enterprises mostly turn towards project management approaches. The major problem is to deal with the complexity resulting from the multifunctional aspect of projects, which needs a clear definition of the objectives and the roles that each agent has to perform. Therefore a sufficiently formalized information system can be an efficient monitoring tool, but despite many project management guidelines, a formal description is not yet available. Thus our aim is to formalize the project approach in terms of an information and decision system based on an enterprise model, which enables us to describe exchange relationships. This article gives an overview of the general project life cycle as we have defined it and a formalized approach of the first stages. For the specification of an enterprise's information system we use, on the one hand, transition systems for a user-friendly description of the behaviour of the real world entities, and, on the other hand, algebraic specifications of abstract data types for proving the coherence of our model. As far as the design stage is concerned, a class model has been chosen that is automatically derived from the algebraic specifications. At the end of this article we present our current research activities, which aim at integrating a multiagent approach on the design stage. The project model we propose follows a clearly defined life cycle, but is, at the same time, modular and flexible, owing to the concepts of recursivity (a project might replace any project stage at any moment) and role (the agents who will actually take over the defined roles have to be found dynamically).