Abstract : This text is considering a modeling business processes as a system. The system brings together people, tools, knowledge, situation and context. For this, we propose to look at the professional gestures as answers relating to an action. We describe the difference between the concepts of processes and procedures. This difference enables us to look at the business process as a cognitive system indexed. It's a system linked to the socio-informational. It's organized as a commonly shared knowledge to serve as a common information system. With our approach, the business process has three functions. The first is organization. It organizes knowledge located. The second is information. It's the source of mediations between the base of knowledge and professional gesture. The third is regulation of the first two. Our view is based on the study of business processes as social and cultural phenomenon reveals a situated action and knowledge shared and distributed. This is an ethnographic approach.