System life cycle and life cycle processes
Introduction to systems engineering - General concepts

The immoderate, and certainly unconscious, use of ellipsis in systems engineering discourse is undoubtedly a major source of confusion in collective understanding. This is particularly true of terms that may refer to a phase of the project (or program) cycle, a stage in the system's life cycle, or a process: for example, the term "integration" may refer to a program phase, a stage in the system's life cycle, or an engineering process. Many other terms contribute to this dilution of meaning: design, verification, validation, qualification, etc.

First of all, let's take a moment to introduce and distinguish between the different concepts of phase, stage and process.

In systems engineering, there are two overlapping histories to consider: the history...