Life Cycle Terms and Concepts: Difference between revisions

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'''''Lead Authors:''''' ''Rick Adcock, Sanford Friedenthal''
'''''Lead Authors:''''' ''Mike Yokell '''Contributing Authors:''' David Endler, Garry Roedler''
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In this Knowledge Area, we introduce the following key principles: life cycle, life cycle model and life cycle processes. A generic SE paradigm is described; this forms a starting point for discussions of more detailed life cycle knowledge.
A life cycle is the evolution of a system, product, service, project or other human-made entity from conception through retirement. (ISO/IEC/IEEE 24748-1:2024) It can be helpful to create models to depict and manage the progression of the entity from beginning to end. These models are called life cycle models. A stage is a period within the life cycle of an entity that relates to the state of its description or realization. Stages relate to major progress, achievement milestones, or decision points of the entity through its life cycle. Technical reviews and audits are a mechanism by which sufficiently independent and knowledgeable stakeholders analyze the current state of a system, work product, or set of work products using pre-established criteria.


==Topics==
==Articles==
Each part of the SEBoK is divided into knowledge areas (KAs), which are groupings of information with a related theme. The Kas, in turn, are divided into topics. This KA contains the following topics:  
This Knowledge Area contains the following articles:  
*[[Generic Life Cycle Model]]
*[[Life Cycle Concepts]]
*[[Applying Life Cycle Processes]]
*[[Life Cycle Models]]
*[[Life Cycle Processes and Enterprise Need]]
*[[Life Cycle Stages]]
See the article [[Matrix of Implementation Examples]] for a mapping of case studies and vignettes included in Part 7 to topics covered in Part 3.
*[[Technical Reviews and Audits]]
 
==References==
==Life Cycle Terminology==
===Works Cited===
The term {{Term|Life Cycle (glossary)}} is one that engineering has borrowed from the natural sciences; it is used to describe both the changes a single organism goes through over its life and how the lives of multiple organisms interact to sustain or evolve a population.  We use it in engineering in the same ways to describe the complete life of an instance of a {{Term|System-of-Interest (glossary)}} (SoI); and the managed combination of multiple such instances to provide capabilities which deliver stakeholder satisfaction.
 
A {{Term|Life Cycle Model (glossary)|life cycle model}} identifies the major {{Term|Stage (glossary)|stages}} that a specific SoI goes through, from its inception to its retirement.  Life cycle models are generally implemented in development projects and are strongly aligned with management planning and decision making.
 
==Generic Systems Engineering Paradigm==  
 
Figure 1 identifies the overall goals of any SE effort, which are: the understanding of stakeholder value; the selection of a specific need to be addressed; the transformation of that need into a system (the product or service that provides for the need); and the use of that product or service to provide the stakeholder value. This paradigm has been developed according to the principles of the [[Applying the Systems Approach|systems approach]] discussed in Part 2 and is used to establish a basis for the KAs in Part 3 and Part 4 of the SEBoK.
 
[[File:062211_BL_Paradigm.png|thumb|center|700px|'''Figure 1. Generic Systems Engineering Paradigm.''' (SEBoK Original)]]
 
On the left side of Figure 1, there are SoI's identified in the formation of a {{Term|System Breakdown Structure (glossary)|system breakdown structure}}. SoI 1 is broken down into its basic elements, which in this case are systems as well (SoI 2 and SoI 3). These two systems are composed of {{Term|System Element (glossary)|system elements}} that are not refined any further.
 
On the right side of Figure 1, each SoI has a corresponding {{Term|Life Cycle Model (glossary)|life cycle model}} which is composed of stages that are populated with processes. The function of these processes is to define the work that is to be performed and the associated artifacts to be produced. In a model-based approach, these artifacts are captured in the system model that represents the SoIs. Note that some of the requirements defined to meet the need are distributed in the early stages of the life cycle for SoI 1, while others are designated to the life cycles of SoI 2 or SoI 3. The decomposition of the system illustrates the fundamental concept of {{Term|Recursion (glossary)|recursion}} as defined in the ISO/IEC/IEEE 15288 standard; with the standard being reapplied for each SoI (ISO 2015). It is important to point out that the requirements may be allocated to different system elements, which may be integrated in different life cycle stages of any of the three SoI's; however, together they form a cohesive system. For example, SoI 1 may be a simple vehicle composed of a chassis, motor and controls, SoI 2 an embedded hardware system, and Sol 3 a {{Term|Software System (glossary)|software intensive}} interface and control system.
STOPPED HERE
When performing SE processes in stages, {{Term|Iteration (glossary)|iteration (glossary)}} between stages is often required (e.g. in successive refinement of the definition of the system or in providing an update or upgrade of an existing system). The work performed in the processes and stages can be performed in a {{Term|Concurrent (glossary)|concurrent}} manner within the life cycle of any of the systems of interest and also among the multiple life cycles.
 
This paradigm provides a fundamental framework for understanding generic SE (seen in Part 3), as well as for the application of SE to the various types of systems described in [[Applications of Systems Engineering|Part 4]].
 
==References==  


 
ISO/IEC/IEEE 24748-1. 2024. ''Systems and software engineering — Life cycle management, Part 1: Guidelines for life cycle management.'' Geneva, Switzerland: International Organization for Standardization (ISO), International Electrotechnical Commission, and Institute of Electrical and Electronics Engineers.  
===Works Cited===
ISO/IEC/IEEE. 2015.''[[ISO/IEC/IEEE 15288|Systems and Software Engineering - System Life Cycle Processes]]''. Geneva, Switzerland: International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC)/Institute of Electrical and Electronics Engineers.[[ISO/IEC/IEEE 15288|ISO/IEC 15288]], 2015.


===Primary References===
===Primary References===


INCOSE. 2015. ''[[INCOSE Systems Engineering Handbook|Systems Engineering Handbook]]: A Guide for System Life Cycle Processes and Activities'', version 4.0. Hoboken, NJ, USA: John Wiley and Sons, Inc. ISBN: 978-1-118-99940-0.
None.
 
Lawson, H. 2010. ''[[A Journey Through the Systems Landscape]].''  London, UK:  College Publications.


===Additional References===
===Additional References===
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<center>[[Model-Based Systems Engineering (MBSE)|< Previous Article]] | [[Systems Engineering and Management|Parent Article]] | [[Generic Life Cycle Model|Next Article >]]</center>
<center>[[Model-Based Systems Engineering (MBSE)|< Previous Article]] | [[Systems Engineering and Management|Parent Article]] | [[Life Cycle Concepts|Next Article >]]</center>


<center>'''SEBoK v. 2.6, released 20 May 2022'''</center>
<center>'''SEBoK v. 2.12, released 27 May 2025'''</center>


[[Category: Part 3]][[Category:Knowledge Area]]
[[Category: Part 3]][[Category:Knowledge Area]]

Latest revision as of 23:58, 23 May 2025

Lead Authors: Mike Yokell Contributing Authors: David Endler, Garry Roedler

A life cycle is the evolution of a system, product, service, project or other human-made entity from conception through retirement. (ISO/IEC/IEEE 24748-1:2024) It can be helpful to create models to depict and manage the progression of the entity from beginning to end. These models are called life cycle models. A stage is a period within the life cycle of an entity that relates to the state of its description or realization. Stages relate to major progress, achievement milestones, or decision points of the entity through its life cycle. Technical reviews and audits are a mechanism by which sufficiently independent and knowledgeable stakeholders analyze the current state of a system, work product, or set of work products using pre-established criteria.

Articles

This Knowledge Area contains the following articles:

References

Works Cited

ISO/IEC/IEEE 24748-1. 2024. Systems and software engineering — Life cycle management, Part 1: Guidelines for life cycle management. Geneva, Switzerland: International Organization for Standardization (ISO), International Electrotechnical Commission, and Institute of Electrical and Electronics Engineers.

Primary References

None.

Additional References

None.

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