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Part III. Appendix 5: System Engineering Approachopment through requirements to operations. Then more requirements are added and the processfrom requirements to operations is repeated through this “spiral” until all requirements are accomplished.A variant of the spiral model is the phased approach. In this method, the system requirements areallocated to phases where a preceding phase may have influence on the subsequent phase requirements.The phases can be executed using a waterfall-like process, i.e. with requirements specification(or update), analysis and design, system development, and verification performed for eachphase. Each phase (sometimes referred to as effectivity), then, would represent a complete end-toendexecution of a subset of the requirements.Figure 1 illustrates the tasks and sequence associated with each phased cycle in the spiral model.After steps one through seven additional requirements are specified and the cycle is repeated.Figure 2 represents a full-blown project implementation following the Spiral Model; this implementationincludes the formalism of the Waterfall Model.Table 2 compares all three types of process models. Based on a review of the Data Management andCommunication Subsystem requirements and a view of the Comparison Table it is recommendedthat the Spiral Model for Systems Engineering be selected.A phased approach that would fit this purpose is shown in Figure 3.277