Project life cycle
However, since it was already clear that we were talking about works, and the natural maximum (proportional to the phases of the lifecycle) unit of work in project management became the "project" (project, not design), another term emerged: the project life cycle, meaning the works of the complete system life cycle that fell within the scope of a specific project. These projects usually coincided with works conducted for some complete stages of the life cycle, one or several. This was a natural division of the life cycle because different projects were often carried out by different organizations - and it was necessary to somehow distinguish parts of the life cycle for which the project organization/unit had responsibility.
In fact, systems thinking and project management/project management were connected like this: life cycle referred to the activities related to the target system that were the subject of project management in various projects regarding the target system.
At that time, systems thinking did not focus much on creation systems (in biology this did not exist, and in technical projects engineers of "hardware", software, and cyber-physical systems rarely thought as carefully about creation systems as they did about target systems, leaving it to managers and company founders/entrepreneurs), so project management as a managerial movement in the 80s and 90s did quite a lot to introduce thoughts into systems thinking not only about the environment but also about creation systems, and methodology from the theory of methods of cognition became a fully-fledged engineering fundamental discipline, including the emergence of methodological standards of the first wave and concepts of methods engineering and situational method engineering[1].
By and large, project roles/stakeholders as a methodological concept were significant in project management: they often formed part of different creation systems as their functional parts! If I am developing a clock gear, then the clock developer (the concept of using clocks, setting the benchmarks for accuracy values, etc., will be the needs for the gear project, the clock concept where he proposed gears instead of electronics), who will accept my results - the implementation of the gear, this role is the external project role of the "customer" for my gear project, and this role may be further divided - a watch designer, a watch production technologist as someone assembling them from ready gears (so the "customer" suddenly breaks down into sub-roles, and besides the engineering roles of the developer and the production technologist, there may also be a manager, financier, lawyer, logistician, etc.). And in the watch project, for all the roles there, it will be the life cycle stage of the watch "creating clock details," where my gear project work will be taken into account. Without introducing the concept of "roles," it is easy to get confused in such a project: who can do what, who influences what, what are the "areas of responsibility," who pays whom for what, who estimates timeframes, who takes these timeframe estimates into account when planning.
Thinking about creators significantly involves the full life cycle of the target system (all works from concept to fine-tuning adjustments), and recently adding an understanding that this is indeed a cycle. People often mention just a life cycle, omitting the words "full" and "target" from the lengthy phrase in the previous sentence. Unless stated otherwise - it refers to the target system and the full life cycle, all life cycles of all projects related to the target system. It can also specify a part of the full life cycle - the project life cycle. However, thinking about creators is not limited to the concept of life cycle, gradually moving away from this concept. Besides the lifecycle description method 1.0, there will be a lifecycle description method 2.0, which will address organizational roles and practices. Also, remember that there is also the element of development/evolution time - where the idea of the "full life cycle" fails because there is the possibility of using it to denote works in the system's development, meaning going through many "full life cycles of the system" within a larger "even more complete life cycle," and more often instead of the concept of "life cycle," people now talk about "creation and development of the system," including even the time of operation/use and disposal of the various resulting variants that became unnecessary during development (simply irrevocable breakdown or even moral aging) of the completed system.
In the initial (1.0) understanding, the life cycle was all about categorizing all works of the creators regarding the conceived, developed, implemented, operated, ceased target system at a macro level. By inertia, this understanding also includes works of development. Whether a single creating organization performs all these works or there are many different organizations engaged in various lifecycle projects - that is less important. The key here is not to forget the completeness of the life cycle, "from birth to death" and even "the cycle of rebirths and deaths, especially when it comes to individual features."