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.