Incremental development if the user requirements are

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Unformatted text preview: cumented at each level. This minimizes the chances that requirements are specified in a way that cannot be measured or verified. Even at the highest levels, as user requirements are translated into system requirements, the system verification approach, which will prove that the system does what is required, must be determined. The technical demands of the verification process, represented as an orthagonal process in Figure 7(c), can drive cost and schedule, and may in fact be a discriminator between alternative concepts. For example, if engineering models are to be used for verification or validation, they must be specified and costed, their characteristics must be defined, and their development time must be incorporated into the schedule from the beginning. Incremental Development. If the user requirements are too vague to permit final definition at PDR, one approach is to develop the project in predetermined incremental releases. The first release is focused on meeting a minimum set of user requirements, with subsequent releases providing added functionality and performance. This is a common approach in software development. The incremental development approach is easy to describe in terms of the vee chart: all increments have a common heritage down to the first PDR. The balance of the product development process has a series of displaced and overlapping vees, one for each release. 3.7.2 The NASA Program/Project Life Cycle Process Flow Another idealized description of the technical activities that occur during the NASA project life cycle is illustrated in Figure 8 (foldout, next page). In the figure, the NASA project life cycle is partitioned into ten process flow blocks, which are called stages in this handbook. The stages reflect the changing nature of the work that needs to be performed as the system matures. These stages are related both temporally and logically. Successive stages mark increasing system refinement and maturity, and require the products of previous stages...
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