SE Life-Cycle Building Blocks
MITRE systems engineers (SEs) orchestrate the complete development of a system, from a need through operations to retirement, by applying a set of life-cycle building blocks. SEs are expected to understand and work with fundamental building blocks for engineering systems, regardless of the specific life-cycle methodology used. They are expected to define systems conceptually, transform user needs into system requirements, and develop and assess architectures. They are expected to compose and assess alternative design and development approaches; develop test and certification strategies; monitor and assess contractor efforts in design, development, integration, and test; and assist with field deployment, operations, and maintenance.
All systems engineering models and processes are organized around the concept of a life cycle. Although the detailed views, implementations, and terminology used to articulate the SE life cycle differ across MITRE's sponsors and customers, they all share fundamental elements.
For example, Department of Defense (DoD) Instruction 5000.02  uses the following phases: materiel solution analysis, technology development, engineering, and manufacturing development, production and deployment, and operations and support; however, this conceptualization of the system life cycle is by no means unique.
ISO/IEC 15288  is an international systems engineering standard covering processes and life-cycle stages. It defines a set of processes divided into four categories: technical, project, agreement, and enterprise. Example life-cycle stages described in the document are: concept, development, production, utilization, support, and retirement. The International Council on Systems Engineering (INCOSE) uses a consistent approach in its Systems Engineering Handbook, version 3.1 .
A V-model  is a common graphical representation of the system engineering life cycle. The left side of the V represents concept development and the decomposition of requirements into function and physical entities that can be architected, designed, and developed. The right side of the V represents integration of these entities (including appropriate testing to verify that they satisfy the requirements) and their ultimate transition into the field, where they are operated and maintained. The model we use in this guide is based on this representation. For each phase, we have written articles that succinctly describe the major activities in each cycle. They are summarized below.
This first phase is concerned with transforming a user's expression of an operational need into a well-defined concept of operations, a high-level conceptual definition, and a set of initial operational requirements. This Systems Engineering Guide (SEG) topic contains the following articles: Operational Needs Assessment, Concept of Operations, Operational Requirements, and High-Level Conceptual Definition.
In this phase, detailed system requirements are elicited from the user and other stakeholders, the requirements are further analyzed and refined, and plans and processes for managing the requirements throughout the rest of the system life cycle are developed. With today's complex systems, there is always a degree of instability and uncertainty with the requirements, so methods to accommodate this are included as well during this phase. This SEG topic contains articles entitled Eliciting, Collecting, and Developing Requirements, Analyzing and Defining Requirements, and Special Considerations for Conditions of Uncertainty: Prototyping and Experimentation.
Once the requirements are expressed and folded into a management process, a system architecture can be described. The architecture will be the foundation for further development, integration, testing, operation, interfacing, and improvement of the system as time goes on. In the system architecture articles, we discuss various architecture patterns (e.g., service-oriented architecture), architectural frameworks (e.g., DoDAF [architectural framework]), and formal processes for developing architectures. This SEG topic contains articles called Architectural Frameworks, Models, and Views; Approaches to Architecture Development, and Architectural Patterns.
System Design and Development
At this point in the system life cycle, a complete and comprehensive description of what and how the system is expected to perform has been developed along with an architectural representation to guide the actual design and development of the hardware, software, and interfaces. This SEG topic contains the following articles: Develop System-Level Technical Requirements, Develop Top-Level System Design, and Assess the Design's Ability to Meet the System Requirements.
During the design and development phase, all of the system's sub-systems are complete. In this next system integration phase, the system's components and its interfaces with other systems are integrated into an operational whole. This SEG topic contains articles entitled Identify and Assess Integration and Interoperability Challenges, Develop and Evaluate Integration and Interoperability (I&I) Solution Strategies, Assess Integration Testing Approaches, and Interface Management.
Test and Evaluation
Because the system is completely designed at this point, it is now necessary to test the system to see if it fulfills the users' needs (verification) and all of the defined requirements (validation). Testing at this phase also involves properties such as reliability, security, and interoperability. This SEG topic contains articles called Create and Assess Test and Evaluation Strategies, Assess Test and Evaluation Plans and Procedures, Verification and Validation, and Create and Assess Certification and Accreditation Strategies.
Implementation, Operations and Maintenance, and Transition
Finally, to ensure a successful transition of the system into the field, plans and procedures must be developed for operations and maintenance. Because the technological underpinnings of a system are constantly changing, product improvements—including the insertion of new technologies—must be planned for.
Other SE Life-Cycle Building Blocks Articles
This topic is a staging area for articles on subjects of relevance to SE Life-Cycle Building Blocks but that don't neatly fit under one of its other topics. In most cases, this is because the subject matter is at the edge of our understanding of systems engineering, represents some of the most difficult problems MITRE systems engineers work on, and has not yet formed a sufficient critical mass to constitute a separate topic.
The system life cycle just described is rarely, if ever, as linear as this discussion might imply. There are often iterative cycles, missing phases, overlapping elements, etc. Additionally, processes and activities may apply to more than one phase in a system life cycle, which are better envisioned as threading through or overarching the other building blocks. For these, a series of articles have been written under a topic called "Other Life-Cycle Building Blocks Articles." These include Spanning the Operational Space—How to Select Use Cases and Mission Threads, Acquiring and Incorporating Post-Fielding Operational Feedback into Future Developments, Test and Evaluation of Systems of Systems, and two articles on modeling and simulation — Verification and Validation of Simulation Models and Affordability, Efficiency, and Effectiveness.
References & Resources:
- Department of Defense Instruction Number 5000.02, December 8, 2008, Operation of the Defense Acquisition System.
- ISO/IEC 15288, 2002, Systems Engineering—System Life Cycle Processes.
- International Council on Systems Engineering (INCOSE), January 2010, INCOSE Systems Engineering Handbook, Version 3.2, INCOSE-TP-2003-002-03.2.
- Wikipedia contributors, "V-Model," Wikipedia, The Free Encyclopedia, accessed January 13, 2010.
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