You may not be familiar with the term “life cycle model”. A life cycle model describes the distinct stages of a system’s “life”. Generally, a system moves through different stages, from planning, concept, development, implementation, operations and support with final retirement. The role of the systems engineer encompasses the entire life cycle of the system. Within the context of the system life cycle stages described above, there are several life cycle approaches used by agencies to develop a technology project. The best development strategy depends on how much you know about the system that you want to implement, whether you have all the funds that you need to implement the system in one fell swoop, your agency and contractor capabilities, and your assessment of the project risks. Several of these life cycle approaches include:
Sequential Methods – Sequential methods are characterized by a system moving through a set of defined processes with gates that are passed through between each process. These gates are usually deliverables such as a Concept of Operations or Requirements document. Traceability between the processes is another trait of a sequential method. Examples of sequential methods are the traditional “waterfall” transportation project development model as well as the Vee model.
Incremental Methods - The most common incremental method is really a variation of a sequential method. It may have incremental aspects relating to design and development of the system, but a key aspect of this approach is that the complete system is initially planned and specified. In this case, you are making one pass through the first part of the development process to determine the needs addressed and the requirements of the system. One or several projects then iterate through the latter part of the development process for each phased increment.
Iterative Methods - There are several development methods that employ iterative approaches throughout the development process. In these methods, developers plan, specify, and implement an initial system capability. Following the initial development, which may or may not be determined acceptable for operational use, this process leverages experience gained with the initial system to define the next iteration to fix problems and extend capabilities.
These iterative approaches are often used when the requirements are unclear from the beginning, or the stakeholder wishes to hold the system of interest open to the possibilities of inserting new technology or capabilities
One type of iterative method, described under the term Agile development, can be considered for use for ITS projects. Agile is a technical development strategy characterized by frequent, incremental deliveries of value. The requirements and architecture for a system of interest are allowed to evolve as development progresses, rather than attempting to fully define them at the beginning of development.
One of the most common iterative methods is referred to as the Scrum method. Scrum is an iterative agile methodology for managing product development within which people can address complex adaptive problems, while productively and creatively delivering products of high value. The original idea of the agile concept was to provide an alternative to the sequential waterfall method for software development, providing an alternative to documentation driven, heavyweight software development processes. The idea was to incrementally deliver planned functionality earlier in the development cycle.
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Document View provides some additional context and detail for SE Lifecycle Models:
· Systems Engineering Life Cycle Models
