AbstractA discussion of the evolution of software system configurations should have some formal basis in order to make the concepts applicable in a broad environment. Formal definitions should be provided for a number of notions associated with this topic including the notions of software system architecture, the restrictions of the software system configurations and the mechanisms used to control the evolution of the structural and functional descriptions. The basis for the logical formalism is a formal description of the transitions that might occur in the software change process, the purpose of the formalism being to allow deductions to be made about the validity of such transitions. Transitions are represented as actions with deontic notions to allow the statement of “permission” and “obligation”. Actions apply to a state model of a change process scenario. This model describes some of the essential features of a configuration management system, that is, versions, and module and subsystem families. Predicates are defined for this model essentially as invariants describing, for example, the relationship between a concrete interface and an abstract interface. We argue the generality of the logical formalism by illustrating its applicability to the expression of change processes in general software descriptions.