Illustration of the life cycle as work (LC 1.0) ​

Representation of life cycles with work periodization was very simple: they were depicted as "sausages" in which large works of certain periods of time were sequentially performed within the overall work period. These large time segments within the overall time of work on changing system states were named life cycle stages/phases. Here are examples of such depictions of life cycles for different types of systems from the standard ISO 15288, and note that each stage name there reflects the behavior/work of the creation systems, not the state of the target system (although sometimes state names are used as an alternative name for the activities to achieve that state, reflecting the principles of PRINCE2 that work should be named based on its results):

The bottom row represents one of the versions of a typical/generic life cycle, which can be defined in one form or another for almost every type of target system. In our course, instead of "idea" we say "conception", instead of "development" and "manufacturing" - a common term for them is "creation", instead of "usage" and "support" - "operation", instead of "decommissioning" - "elimination/disposal." You can also suggest your own version: the main thing here is that the life cycle extends to both work on system descriptions and work on system realization. However, in this first generation, it usually does not yet include work with the creation systems themselves (recording creation chains, creating creation systems by other creation systems): to build a nuclear power plant or a bridge, construction needs to be organized, a whole town needs to be built at the construction site, necessary construction equipment needs to be delivered there. And if something completely new is being developed, sometimes a project institute needs to be created, not just a construction site. These are all creation chains, crucial for consideration in modern systems thinking, and planning their work is also essential. But here we are still talking about the first generation - this "first-generation" understanding is still widely used, engineers and managers who obtained education twenty years ago still use it extensively, the literature is full of these "sausages," so you need to understand this first-generation understanding of the life cycle at least to communicate with these people.

In the "sausage" diagrams of the life cycle, the stages "usage/operation" and "support/maintenance and repairs" are often shown not sequentially, but in the same place of the "sausage" (or the name in one "slice" of the sausage, as shown in the picture, or even the slice is divided into two "overlapping stages," two halves horizontally). At this point, it must be acknowledged that life cycle stages do not necessarily follow each other sequentially; they can overlap - meaning that activities of different stages can be carried out at the same time.

Here is the same life cycle, but here instead of sausage slices, "right-facing chevrons" are used, denoting a "process" with sequential stages as process steps. Representing the life cycle as a sequence of works emphasizes the unfolding in time, this is a "procedural," rather than a "declarative" description of creation system works of the target system. Work descriptions are one of the descriptions of creation systems. "Design" (work on designing the target system) makes up the creation system, not the target system. Work descriptions relate to what creation systems do, not what the target system does:

In this picture, it is not possible to indicate precise moments when one process starts and another ends, and this is intentional - the arrow of one stage literally enters the tail of another stage so that a vertical line cannot be drawn clearly separating one "right-facing chevron" from another. Sometimes this fact of blurred transition time between stages is reflected by the sausage slices being divided not by straight lines, but by diagonal ones - indicating that the works of one stage are slowly finishing while works of another stage are slowly starting, there is no moment of abrupt cessation of one stage's works and a sharp beginning of other stage's works. This more accurately corresponds to what is seen in practice: there are usually many works in each stage, and when works of one stage start (for example, the manufacturing of some parts/components/subsystems of the future system begins), works of another stage may still be ongoing (for example, the design of other components of the future system is not completed yet).

The term "life cycle" always implies a "complete" cycle, that is, from the works of creation systems according to conception to the works of termination/existence cessation/liquidation/disposal/out of operation of the post-operated target system. These are all the works of the creators because the target system doesn't conceive itself, it is the creators who conceive it! The same goes for other stages, usually systems do not create themselves, do not operate themselves, do not get rid of themselves. This is where the strength of the systemic approach lay, the term itself indicated thinking about the complete life cycle, all necessary works, not just about its separate parts-stages, not about the works carried out with the target system! The term "life cycle" indicated thinking about the works conducted by the creation systems in their chains, not only about systems in the operational environment of the target system. Mentioning the life cycle made us pay due attention to the organization/team/collective of the project’s works with the creation systems.

The methodology (discussing ways of performing works, not just the sequence of performing works and grouping works into stages/phases) came a little later. The idea of the insignificance of the creators (for example, the concept of creator from constructor theory by David Deutsch) came even later, largely this idea has not yet entered the methodological mainstream, it is still on the frontier. And even later came the idea that a one-time design-manufacture is not enough, systems evolve, they continuously develop - but not so much are evolving by themselves, as they are developed by their creators.