Software evolution in the era of software services

Software evolution has been traditionally associated with the idea of changing the code of a system, or system´s component. It is universally accepted that software must be continually changed to remain satisfactory in use and evolution is often seen as the long term result of software maintenance. In This work, I argue that replacement, in addition to change, be considered as a basic mechanism for software evolution. In other words, the traditional approach to evolving a software system by changing its components should be contrasted with the alternative of replacing the individual components. This entails a shift of perspective from the current situation, where a need for a new/modified characteristic of a system raised by the business entails a change request to the system´s supplier, to the situation in which the same need entails disengaging the affected system´s components and searching the marketplace for replacement components that meet the new needs. The paper discusses motivations for such a change of perspective and shows how service oriented architectures can support it.