An old hobbyhorse of mine: I believe that author Robin Hornby is as confusing on the question of "cycles" as is the PMBOK® Guide. He says in his Chapter Synopsis:
"Evolution of a Business Life Cycle: Shows how the tenets of the PMBOK® Project Management Process Groups can be evolved into a universal business lifecycle, and why this is the foundation for all that follows. Integrates a functional model of project management based on Planning, Organizing, Controlling, and Leading. Calls for a renewed focus on the application lifecycle as a basis for integration of project management functions and all project deliverables."
Let's look at that more closely. Firstly, the author is referring to some "Business Lifecycle" and is in danger of confusing this with a business's normal "Annual Business Cycle". The "Annual Business Cycle" is designed to satisfy the legislative accounting requirements of the jurisdiction in which the project execution takes place. Secondly, the "PMBOK® Project Management Process Groups" are indeed cyclical. They repeat as necessary as an over arching management process. But that should not be confused with the "project life cycle" which itself is a misnomer and should more properly be called a "Project Life Span". As such, it does not go through a "cycle".
It may be argued that software products go through endless upgrade cycles. True, but each upgrade should be managed as a separate project (or subproject, as in a "program" if you must).
Thirdly, Robin says: "Integrates a functional model of project management based on Planning, Organizing, Controlling, and Leading. Calls for a renewed focus on the application lifecycle as a basis for integration of project management functions and all project deliverables." To the novice reader, we suspect that this is implying that the "Planning, Organizing, Controlling, and Leading" referred to, is the project life span. The PMBOK Guide does make it clear that this is not the case, though their choice of labels is certainly confusing.
However, Robin's reference to the "application lifecycle" (let's call that "lifespan") is important because it implies that different areas of project management application do have different lifespans. And that is what makes Robin's proposed Commercial Delivery Methodology, as a basis for the layout of Part 2 of his book, a unique source of reference.
12. Ibid, p6