Our research deals with a particular class of cooperative applications, which aggregate several partners around a common project, and for the duration of this project. Cooperation in these applications occurs in the most common case through the sharing of persistent objects: the products of the project. Partners share and modify these products, alternating periods of isolated work with periods of interaction. This paper introduces a formal framework to specify in temporal logic such interactions in a simple way by combining basic cooperation modes. A cooperation mode results from a combination of dependencies between two activities with regards to an object, or from the combination of cooperation modes in a more complex one. Dependencies are expressed as logical predicates. Complex interactions and cooperation modes are thus described as temporal logic formulae built from these predicates.