An emerging methodology of organizing systems-engineering plans is based on a concept of core and off-core processes or activities. This concept has emerged as a result of recognition of a risk in the traditional representation of systems-engineering plans by a Vee model alone, according to which a large system is decomposed into levels of smaller subsystems, then integrated through levels of increasing scope until the full system is constructed. Actual systems-engineering activity is more complicated, raising the possibility that the staff will become confused in the absence of plans which explain the nature and ordering of work beyond the traditional Vee model.
Core activities are those that produce a top-down decomposition and bottoms-up integration of a system in order of increasing time. Examples of core activities are definition of requirements, design, acquisition, and integration. Because of ordering according to time, these activities are often readily understood and depicted by use of such elementary graphical aids such as timelines and Gantt charts.
Off-core activities are other systems-engineering activities that add desirable qualities to a system solution, but are not directly involved in decomposition and integration. Examples of off-core activities are management of risk and opportunity, verification, validation, and troubleshooting. Because these activities are usually repeated many times and may not inherently be ordered in the same way as the core processes, they often cannot be represented by use of simple graphical aids. The complexity and difficulty of the task of representing off-core activities is increased by the fact that the timing and type of work involved in these activities are more unpredictable than are those of core activities.
In the present methodology, as applied to the development of a given system, the systems-engineering plan is organized to explicitly treat core and off-core activities separately. This approach to organization provides a conceptual framework that can facilitate and accelerate understanding, by members of the systems-engineering staff, of the relationships among many parallel activities. In so doing, this approach can reduce the difficulty of coordinating those activities.