Introduction

The SEBOK divides the traditional life cycle process steps into four stages. This chapter will discuss the realization stage. The processes included in realization are those required to build a system, integrate disparate system elements, and ensure that the system both meets the needs of stakeholders and aligns with the requirements identified in the system definition stages. These processes are not sequential; their iteration and flow are depicted in Figure 1, which also shows how these processes fit within the context of the System Definition and System Deployment and Use knowledge areas.

Essentially, the outputs of system definition are used during implementation to create system elements and during integration to provide plans and criteria for combining these elements. The requirements derived as part of system definition are used to verify and validate elements, subsystems, and the overall system. These activities provide feedback into the system design, particularly when problems or challenges are identified. Finally, when the system is considered verified and validated, it will then become an input to system deployment and use. It is important to realize that there is overlap in these activities; they do not have to occur in sequence. The way these activities are performed is dependent upon the life cycle model in use (for additional information on life cycles, please see the Systems Engineering Life Cycles knowledge area (KA).

The realization processes are designed to ensure that the system will be ready to transition and have the appropriate structure and behavior to enable desired operation and functionality throughout the system’s life span. Both DAU and NASA include “transition” in realization in addition to implementation, integration, verification, and validation. (Prosnik 2010; NASA December 2007, 1-360) However, the SEBoK includes transition in the System Deployment and Use KA.

Topics presented under realization include:

Fundamentals
Implementation
Integration
Verification
Validation

Fundamentals

Figure 2 illustrates a macro view of generic outputs from realization activities when using a Vee life cycle model. The left side of the Vee represents various design activities 'going down' the system. File:The V - A Macro View.png

The left side of the Vee model demonstrates the development of end-product specifications and design descriptions. In this stage, verification and validation plans are developed which are later used to determine whether realized products are compliant with specifications and stakeholder requirements. Also during this stage, initial specifications become flow-down requirements for lower-level system models. In terms of time frame, these activities are going on ‘early’ in the system’s life cycle. Many of these activities are discussed in the System Definition knowledge area. However, it is important to realize that some of the system realization activities are initiated at the same time as some system definition activities.

The right side of the Vee model, as illustrated in Figure 2, results in system elements that are assembled into end products according to the system model described during the left side of the Vee. Verification and validation activities determine how well the system fulfills the stakeholder requirements and design specifications. These activities should follow the plans developed on the left side of the Vee.

The U.S. Defense Acquisition University (DAU) provides this overview of what occurs during system realization:

"Once the products of all system models have been fully defined, Bottom-Up End Product Realization can be initiated. This begins by applying the Implementation Process to buy, build, code or reuse end products. These implemented end products are verified against their design descriptions and specifications, validated against Stakeholder Requirements and then transitioned to the next higher system model for integration. End products from the Integration Process are successively integrated upward, verified and validated, transitioned to the next acquisition phase or transitioned ultimately as the End Product to the user." (Prosnik 2010)

While the systems engineering technical processes are life cycle processes, the processes are concurrent, and the emphasis of the respective processes depends on the phase and maturity of the design. Figure 3 demonstrates (from left to right) a notional emphasis of the respective processes throughout the systems acquisition life cycle from the perspective of the U.S. Department of Defense (DoD). It is important to note that, from this perspective, these processes do not follow a linear progression. Instead, they are concurrent, with the amount of activity in a given area changing over the system’s life cycle. The red boxes indicate the topics that will be discussed below as part of realization.

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