Evolving requirements through coordination contracts

Use-case driven software development processes can seriously compromise the ability of systems to evolve if a careful distinction is not made between "structure" and "use", and this distinction is not reflected immediately in the first model and carried through to the implementation. By "structure", we are referring to what derives from the nature of the application domain, i.e. to what are perceived to be the "invariants" or core concepts of the business domain, as opposed to the business rules that apply at a given moment and determine the way the system (solution) will be used. This paper shows how the notion of coordination contract can be used to support the separation between structure and use at the level of system models, and how this separation supports the evolution of requirements on "use" based on the revision or addition of use cases, with minimal impact on the "structure" of the system.