Using the example of distributed requirements engineering process in the PROART environment, we characterize some principles for a-priori process integration of cooperative information systems. Allowed interoperations between subsystems (in PROART: RE tools) are explicitly defined in a process model. This model is used to control and support the cooperation between different actors during process execution. In the case of requirements engineering, process orientation of tools enables an explicit support for the distribution and integration along the dimensions of representation, domain knowledge, and stakeholder agreement. In the general case of cooperative information systems, it enables controlled use of information resources depending on the actor or/and process the actor is involved in.