Difference between revisions of "Introduction to Life Cycle Processes"

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'''''Lead Authors:''''' ''Rick Adcock, Sanford Friedenthal''
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In this Knowledge Area we introduce key principles of 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.
 
In this Knowledge Area we introduce key principles of 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.
  
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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:  
 
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:  
 
*[[Generic Life Cycle Model]]
 
*[[Generic Life Cycle Model]]
*[[Applying SE across the Enterprise]]
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*[[Applying Life Cycle Processes]]
*[[Applying Iteration and Recursion to the Life Cycle]]
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*[[Life Cycle Processes and Enterprise Need]]
*[[Lean Engineering]]
 
 
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.
 
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.
  
 
==Life Cycle Terminology==
 
==Life Cycle Terminology==
The 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 it 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 [[System-of-Interest (glossary)]] (SoI); and the managed combination of multiple such instances to provide capabilities which provide stakeholder satisfaction.
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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 it 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 [[Life Cycle Model (glossary)|life cycle model]] identifies the major [[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.
 
 
 
A [[Process (glossary)|process]] is a series of actions or steps taken in order to achieve a particular end; as a verb it is the performing of the operations.  Processes can be performed by humans or machines transforming inputs into outputs.
 
  
In SEBoK processes are interpreted in several ways, including: technical, life cycle, business, or manufacturing flow processes.  Many of the Part 3 sections are structured along technical processes (e.g. design, verification); however, [[Life Cycle Models]] also describes a number of high level program life cycle sequence which call themselves processes (e.g. rational unified process (RUP), etc.).
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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.
 
 
[[Applications of Systems Engineering|Part 4: Applications of Systems Engineering]] and [[Enabling Systems Engineering|Part 5: Enabling Systems Engineering]] utilize processes that are related to services and business enterprise operations.  
 
 
 
Systems Engineering [[Life Cycle Process (glossary)]] define technical and management activities performed across one or more stages to provide the information needed to make life cycle decisions; and to enable to realization, use and sustainment of systems across the life cycle as necessary.  This relationship between life cycle model and process activities can be used to describe how SE is applied to different system contexts.
 
  
 
==Generic Systems Engineering Paradigm==  
 
==Generic Systems Engineering Paradigm==  
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[[File:062211_BL_Paradigm.png|thumb|center|700px|'''Figure 1. Generic Systems Engineering Paradigm.''' (SEBoK Original)]]
 
[[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 [[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 [[System Element (glossary)|system elements]] that are not refined any further.
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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 [[Life Cycle Model (glossary)|life cycle model (glossary)]] which is composed of the stages that are populated with processes. The function of these processes is to define the work that is to be performed. 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 [[Recursion (glossary)|recursion (glossary)]] as defined in the ISO/IEC 15288 standard; with the standard being reapplied for each SoI (ISO/IEC 15288). 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 [[Software System (glossary)|software intensive]] interface and control system.  
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On the right side of Figure 1, each SoI has a corresponding {{Term|Life Cycle Model (glossary)|life cycle model (glossary)}} 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 represent the SoI's. 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 (glossary)}} 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.  
  
When performing SE processes in stages, [[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 [[Concurrent (glossary)|concurrent]] manner within the life cycle of any of the systems of interest and also among the multiple life cycles.
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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]].
 
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]].
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===Primary References===
 
===Primary References===
  
INCOSE. 2012. ''[[INCOSE Systems Engineering Handbook | Systems Engineering Handbook]]'', version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE). INCOSE-TP-2003-002-03.2.2. 
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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
  
 
Lawson, H. 2010. ''[[A Journey Through the Systems Landscape]].''  London, UK:  College Publications.
 
Lawson, H. 2010. ''[[A Journey Through the Systems Landscape]].''  London, UK:  College Publications.
  
 
===Additional References===
 
===Additional References===
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None.
 
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<center>[[Systems Engineering and Management|< Previous Article]] | [[Systems Engineering and Management|Parent Article]] | [[Generic Life Cycle Model|Next Article >]]</center>
 
<center>[[Systems Engineering and Management|< Previous Article]] | [[Systems Engineering and Management|Parent Article]] | [[Generic Life Cycle Model|Next Article >]]</center>
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<center>'''SEBoK v. 2.1, released 31 October 2019'''</center>
  
 
[[Category: Part 3]][[Category:Knowledge Area]]
 
[[Category: Part 3]][[Category:Knowledge Area]]
{{DISQUS}}
 

Latest revision as of 01:02, 26 October 2019


Lead Authors: Rick Adcock, Sanford Friedenthal


In this Knowledge Area we introduce key principles of 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.

Topics

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:

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.

Life Cycle Terminology

The term life cyclelife cycle is one that engineering has borrowed from the natural sciences, it is used to describe both the changes a single organism goes through over it 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 system-of-interestsystem-of-interest (SoI); and the managed combination of multiple such instances to provide capabilities which deliver stakeholder satisfaction.

A life cycle modellife cycle model identifies the major stagesstages 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 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.

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 system breakdown structuresystem 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 system elementssystem elements that are not refined any further.

On the right side of Figure 1, each SoI has a corresponding life cycle model (glossary)life cycle model (glossary) 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 represent the SoI's. 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 recursion (glossary)recursion (glossary) 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 software intensivesoftware intensive interface and control system.

When performing SE processes in stages, 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 concurrentconcurrent 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 Part 4.

References

Works Cited

ISO/IEC/IEEE. 2015.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 15288:2015.

Primary References

INCOSE. 2015. '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

Lawson, H. 2010. A Journey Through the Systems Landscape. London, UK: College Publications.

Additional References

None.


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SEBoK v. 2.1, released 31 October 2019