System Life Cycle Models

A life cycle for a system generally goes through a set of stages, which are usually regulated by a set of management decisions confirming that the project is mature enough to leave one stage and enter another. Frequently, portions of the systems may go through these stages on different timescales, such as with a mobile phone basic platform that will be incorporated into multiple hand set instances. Different phones in the family may have different features and different hardware/software designs (e.g., for cameras, Global Positioning Satellite (GPS), or keyboards), and may be developed on different timelines. Another example is a vehicle platform and its several classes of payloads or mission equipment. The nature of the mission equipment elements may not be fully known in advance, so that the elements will be defined, developed, and joined to the system in a number of evolutionary increments. Still, each element can be considered as a System-of-Interest, and it will go through a generic set of stages such as those depicted in Figure 0 1. But for complex systems whose elements are evolving on different timescales, much

Figure 0 1 – Conceptual Life Cycle Transformations (System-of-Interest Versions)

Note: For many systems the various system versions are developed either concurrently or evolved via multiple iterations between stages. (Lawson 2010, 124)

more nuanced definitions of complex-system “stages” will need to be defined to be able to synchronize all of their evolutionary increments. Also it is critical for the project team to focus at the outset on key operational issues such as maintenance (design for maintainability) and late-stage requirements such as disposal. Note: the Development Stage often, but not exclusively, includes realization of a prototype, thus the boundary between Development and Production is indicated with dotted lines in Figure 0-1.

At the top of Figure 0 1, the System-of-Interest is first described in terms of desired capabilities, along with evidence that they should be feasible to develop and cost-effective to employ. The desired capabilities are then transformed into specific requirements and a solution architecture, again with evidence of feasibility and operational cost-effectiveness. The architecture is then used to develop Defined Physical and/or Human Activity Systems when they become a product, which is again tested and evaluated for cost-effectiveness and instantiated for utilization. An eventual retirement of a System-of-Interest involves disposing of instances and can also involve retirement of the system definition, that is, the Defined Abstract Systems. Note that in the life cycle portrayal the intermediate work products developed during the life cycle are identified as systems in their own right that identify various views of the System-of-Interest. In some cases, organizations with the authority and ability to control the definition and sequencing of the various elements of a system can and should organize the product and the process to treat it as a single System-of-Interest. In such cases, large, complex projects such as designing and producing an aircraft like the Boeing 787 or the Airbus A380, with their worldwide distributions of suppliers and subcontractors, can be defined and managed as a single system. Example families of systems would be variants of the basic passenger aircraft for different national airlines or classes of service, or for non-passenger variants such as tanker or cargo versions. However, even such large Systems-of-Interest will need to operate within one or generally more systems of systems such as the airport system (runways, terminal buildings, related ground support equipment, and human-intensive services such as handling airport security or disabled passengers), the end-to-end transportation system for passengers or cargo, and the various national and international air traffic control systems, which may be evolving on different modernization timescales such as for transitioning to a Global Positioning Satellite (GPS) system for in-flight navigation (NextGen). In such cases, processes oriented around a centrally-controlled individual System-of-Interest cannot provide realistic guidance at the system of (independently evolving) systems level.

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