Validation and verification vs. The software life cycle(Position Statement)

In attempting to forecast the future trends in software engineering, a very dynamic future appears to be in store. Validation and verification are rapidly becoming recognized as an integral part of the total software life cycle. Validation and verification are no longer being viewed as new names for testing. A modern view of validation and verification encompasses the set of tasks and functions needed for tracing requirements through the evolving stages of the system life cycle down to the final implemented code. At each stage of program development, verification of each successively developed representation back to the next higher level representation needs to be performed. Validation is a separate functional activity which also needs to be performed. The main difference between validation and verification is, instead of examining the mapping between representations, an attempt is made to ensure the system will correctly implement the users preceived requirements; the principle question being: Is the system usable?

Thus, validation and verification are not activities which occur merely at the end of the coding process. Validation and verification involve such issues as verifying the preliminary design document back against its requirements, verifying a detailed design document back against a preliminary design document, verifying the code back to the detailed design. Each of these verification exercises is an attempt to provide a trace between the evolving stages of the system. Validation of the developing design occurs in parallel with system evolution. The preliminary designs is validated by the user, the detailed design ramifications are also presented to the user for validation as is the actual operation of the code. This expanded view of validation and verification is not without its problems. Several examples will begiven.