McAfee Secure

Systems Engineering Activity

Exam: CISSP - Certified Information Systems Security Professional

Systems Engineering Activity: System Design
The SE relies on the system architecture plans to define and finalize the system design. That is, the system design should follow what has been outlined as the subsystems or component items (CIs) in the architecture.

The objective for the SE is to design the component parts of the system so they will fit together as an operating whole during the implementation phase. According to Kossiakoff and Sweet (2003), typical functional and component design activities include:

Analyzing component interactions and interfaces and identifying design, integration, and test issues

  • Analyzing detailed user interaction modes
  • Designing and prototyping user interfaces
  • Laying out preliminary design of all hardware and software components and interfaces
  • After review, implementing detailed hardware designs and software code
  • Building prototype versions of engineered components (p. 241-242)

It is assumed that the primary allocation of functions was accomplished in the earlier phases, but the definition of their interactions has not been finalized. Thus, a primary objective of the design phase is to finalize the interactions of components with one another and with the system environment.

This final design includes aspects such as recommendations for acquisition of components, configuration of components, integration, and operation and maintenance of the components.

The concept of trade-off analysis and system level synthesis. The system specifications activity documents the technical requirements for the system and its components. The next topic reviews the design activities according to IEEE 1220:1998, IEEE Standard for Application and Management of the Systems Engineering Process.

Trade-Off Analysis
An important element of the design phase is when the SE analyzes the design constraints and thinks about any trade-offs that may be needed to meet the system requirements. The process of analyzing alternatives and selecting the appropriate solution is generically called a trade-off analysis. This analytical process involves considering the alternatives and balancing the requirements prior to selecting the appropriate solution. The trade-off analysis should help decision makers make decisions, not be a decision maker.

System Synthesis (Design)
According to Blanchard and Fabrycky (1998), the trade-off analysis leads to synthesis , which is the combining and structuring of components in such a way as to represent a feasible system configuration. At the synthesis point, the basic requirements are established, trade-off studies are completed, and a baseline configuration is developed to demonstrate the design concepts. The synthesis is the design - it describes the build-to requirements for the system elements. It defines, refines, and integrates the configuration items into a physical configuration that satisfies the system requirements. It is used in the development of preliminary concepts and to establish relationships among the various components of the system.

During the synthesis of the system, alternate configurations or architectures are developed and evaluated against the system requirements. Prototypes or models can be constructed to support trade-off analysis or valid alternatives. Synthesis takes these alternatives and develops the preliminary concepts and establishes the relationships between system elements. At this step in the process, synthesis establishes a system configuration that is representative of the final system form, sometimes referred to as the system specification document.

System Specifications
The technical requirements for the system and its components are documented through a series of specifications called the system specifications. The system specifications is a document containing the functional baseline and results from various SE activities, such as the needs analysis, feasibility analysis, operational requirements, top-level functional analysis (which may lead to subordinate specifications), maintenance concept, system requirement analysis, and critical technical performance measures.