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The basic tenets of systems development are continual refinement and increasing definition of the system over time. The figure [Figure 3‑2] below illustrates the relationship of each phase of the life cycle to the detail needed for system definition and the refinement of needs, goals, objectives, and expectations. The life cycle of the system may also be viewed as a spiral where each whorl is an increased level of system definition. The first whorl is used to identify the portion of the regional architecture to be developed then gather a comprehensive set of needs, goals, objectives, and expectations. The second whorl analyzes and prioritizes these items, evaluates alternative solutions, and creates the business case through a benefits analysis of the recommended project. The third whorl [above the Vee] is the development phases of the project. This generates the needed system definition to develop, implement, operate, and maintain the project. Finally, the whorls continue throughout the life of the system and represent the upgrades and evolution of the system until its retirement.
It is important to use a top down successive refinement of the set of goals, objectives, needs, envisioned solutions, and expectations for each phase of the life cycle of ITS projects for the following reason.
Whorl 1 – Its purpose is to gather a comprehensive set of goals, objectives, needs, expectations, and envisioned solution.
At the beginning [when the regional architecture is being developed] it is important to be as inclusive as possible concerning the stakeholder’s needs for the envisioned solutions. This generates a large number of needs at a very high level [user services, market package, major information flows]. It also ensures, as much as possible, that nothing is missed as the project moves forward.
Whorl 2 – Its purpose is to prioritize and analyze [cost/benefit] the set of potential concepts.
The next level of refinement takes place in the concept exploration and feasibility phase. Analysis is done for alternative concepts. This analysis identifies the relative costs and benefits of the alternative project concepts. It recommends a concept to move forward into development. This analysis refines the envisioned solutions and prioritizes the goals, objectives, needs, and expectations. The stakeholders are involved in the selection of the recommended concept that will be moved forward into development.
Whorl 3 – Its purpose is to build a project that meets stakeholder needs.
The next level of refinement occurs throughout the project development. During the Concept of Operations, the envisioned solution [recommended system concept] is modeled for its operations from multiple stakeholder viewpoints. As a result, the needs, goals, and information for a system become very specific. The maintainers, operators, and managers will have very specific needs and ideas about the way they would like the system to meet those needs.
Whorls 4 & 5 – Their purpose is to adjust and “fine tune” the system through modifications and upgrades in order to build on the synergy of the system and look for new opportunities.
The final and on-going level of refinement is in the continuous improvement features of the system. The existing system provides an opportunity to define new needs based on real world experience in the use of the system. It also provides the opportunity to adapt the system to the changes in the environment and the stakeholder needs. For example, the changeable message sign system has been adapted to function as an Amber Alert system [new need].
With each phase of the project, the definition of the system becomes clearer. There should be a convergence in stakeholder consensus on needs, objectives, and priorities. In a multi-regional system, this takes time since sharing of information and control may encounter institutional barriers, as well as any natural resistance to change. Each stakeholder must become comfortable with these concepts. Internal policies may need to be changed to support them. This iterative approach enables the stakeholders to identify and address these kinds of issues early. If some of these concepts cannot be implemented, the stakeholders must understand the constraints before projects are started or defined.
Figure 3-2 Spiral Nature of Systems Development
Figure 3‑3 shows the relationship between the life cycle tasks and the Vee Development Model. As shown, the Vee Development Model includes the same development phases that are shown in the life cycle. The Vee Development Model will be used in the remainder of this Guidebook.
Figure 3-3 Transition from the Linear Systems Life cycle to the Vee Technical Development Model