In this paper we propose an approach which allows to define the Requirement Engineering step of a Cooperatif Information System. We used a notion of software engineering: the viewpoints. CIS is a complex system, it involves the cooperation of many stakeholders in a common purpose and each with their own viewpoint. This is why we used the notion of viewpoints, in order to decompose and partition the needs of a CIS according to the viewpoint of each stakeholder, to simplify its modeling. This approach define a meta-model of viewpoint that will allow us to instance the necessary viewpoint to define the needs and requirements of a CIS.