In this paper, we are interested in interenterprises cooperation based on web services and emerged problems. On one hand, the dynamic and non-deterministic nature of cooperation requires both flexibility and elasticity of the process that supports this cooperation. On the other hand, the current Web services emergence, and the new requirements and challenges of interenterprises cooperation (due to virtual enterprises achievement) lead to face and solve the problem of finding a compromise between transparency and confidentiality. In this paper, we introduce a generic object-oriented metamodel for cooperative processes. This metamodel will be used as a basic micro-core for both cooperative processes description (trying to face problems raised above), and inter-enterprises cooperative processes modelling. We present a process abstraction, named service process, allowing enterprises to externalize their business processes as web services while mastering the compromise between transparency and confidentiality.