Difference between revisions of "Vee Life Cycle Model"

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There are a large number of life cycle process models. These models fall into three major categories:
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'''''Lead Authors:''''' ''Dick Fairley, Kevin Forsberg'', '''''Contributing Author:''''' ''Ray Madachy, Phyllis Marbach''
#Primarily Prespecified and Sequential Processes.   
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#Primarily Evolutionary and Concurrent Processes.  Examples are the Rational Unified Process and various forms of the Vee and spiral models.
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There are a large number of [[Life Cycle Models|life cycle process models]]. As discussed in the [[System Life Cycle Process Drivers and Choices]] article, those models described fall into three major categories: (1) primarily pre-specified single-step or multistep, also known as traditional or sequential processes; (2) evolutionary sequential (or the Vee Model)  and (3) evolutionary opportunistic and evolutionary concurrent (or incremental agile)The concurrent processes are known by many names: the agile unified process (formerly the Rational Unified Process), the spiral models) and include some that are primarily interpersonal and unconstrained processes (e.g., agile development, Scrum, extreme programming (XP), the dynamic system development method, and innovation-based processes).
#Primarily Interpersonal and Unconstrained Processes. Examples are Agile development, Scrum, eXtreme Programming, Dynamic System Development Method, and innovation-based processes.
 
 
 
This article discusses the Vee model as the primary example of the first category.  The second two are discussed in the article [[System Life Cycle Process Models: Iterative]]. 
 
  
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This article specifically focuses on the Vee Model as the primary example of pre-specified and sequential processes. In this discussion, it is important to note that the Vee model, and variations of the Vee model, all address the same basic set of systems engineering (SE) activities. The key difference between these models is the way in which they group and represent the aforementioned SE activities.
  
==A Primarily Prespecified and Sequential Process Model: The Vee Model==
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General implications of using the Vee model for system design and development are discussed below; for a more specific understanding of how this life cycle model impacts systems engineering activities, please see the other knowledge areas (KAs) in Part 3.
  
The sequential version of the Vee model is shown in Figure 1. Its core involves a sequential progression of plans, specifications, and products that are baselined and put under configuration management. The vertical two-headed arrow enables projects to perform concurrent opportunity and risk analyses, and continuous in-process validation.
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==A Primarily Pre-specified and Sequential Process Model: The Vee Model ==
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The sequential version of the Vee Model is shown in Figure 1. Its core involves a sequential progression of plans, specifications, and products that are baselined and put under configuration management. The vertical, two-headed arrow enables projects to perform concurrent opportunity and risk analyses, as well as continuous in-process validation. The Vee Model encompasses the first two life cycle stages listed in the "Generic Life Cycle Stages their purposes, and decision gate options" table of the INCOSE ''Systems Engineering Handbook'': concept, and development (INCOSE 2015).
 
   
 
   
[[File:KF_VeeModel_Left.png|500px|Left side of the Vee model (Forsberg, Mooz, and Cotterman 2005. Pg 111)]]
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[[File:KF_VeeModel_Left.png|thumb|center|450px|''Figure 1.'' Left Side of the Sequential Vee Model (INCOSE 2015, adapted from Forsberg, Mooz, and Cotterman 2005, Reprinted with permission of John Wiley & Sons Inc. All other rights are reserved by the copyright owner.]]
 
 
Figure 1 – Left side of the sequential Vee model (Forsberg, Mooz, and Cotterman 2005. Pg 111)
 
 
 
  
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The Vee Model endorses the INCOSE ''Systems Engineering Handbook'' (INCOSE 2015) definition of life cycle stages and their purposes or activities, as shown in Figure 2 below.  Replace Figure 2 with the updated figure that removes the first Exploratory stage.
  
The Vee model endorses the INCOSE Systems Engineering Handbook 2011 definition of life cycle stages and their purposes or activities, as shown in Table 1.  
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[[File:Fig_2_Life_Cycle_Stages_Vee_KF.png|thumb|500px|center|'''Figure 2. An Example of Stages, Their Purposes and Major Decision Gates.''' (SEBoK Original)]]
  
[[File:Generic_life_cycle_stages,_their_purposes,_and_decision_gate_options.PNG|650px|Generic life cycle stages, their purposes, and decision gate options(INCOSE Systems Engineering Handbook 2011, p 25; also ISO/IEC 15288:2008)]]
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A more detailed version of the Vee diagram incorporates life cycle activities into the more generic Vee model. This Vee diagram, developed at the U.S. Defense Acquisition University (DAU), can be seen in Figure 3 below. 
  
Table 1 - Generic life cycle stages, their purposes, and decision gate options
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[[File:JS_Figure_2.png|thumb|600px|center|'''Figure 3. The Vee Activity Diagram (Prosnik 2010).''' Released by the Defense Acquisition University (DAU)/U.S. Department of Defense (DoD).]]
(INCOSE Systems Engineering Handbook 2011, p 25; also ISO/IEC 15288:2008)
 
  
 
===Application of the Vee Model===
 
===Application of the Vee Model===
Lawson (2010) elaborates on the activities in each life cycle stage, and notes it is useful to consider the structure of a generic life cycle stage model for any type of System-of-Interest as portrayed in Figure 2 (Lawson 2010). This (T) model indicates that one or more Definition stages precede a Production stage(s) where the implementation (acquisition, provisioning or development) of two or more system elements has been accomplished.
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Lawson (Lawson 2010) elaborates on the activities in each life cycle stage and notes that it is useful to consider the structure of a generic life cycle stage model for any type of system-of-interest (SoI) as portrayed in Figure 4. This '''(T)''' model indicates that one or more definition stages precede a production stage(s) where the implementation (acquisition, provisioning, or development) of two or more system elements has been accomplished.
  
[[File:KF_GenericStageStructure.png|600px|Generic (T) Stage Structure of System Life Cycle Models]]
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[[File:KF_GenericStageStructure.png|thumb|center|660px|'''Figure 4. Generic (T) Stage Structure of System Life Cycle Models (Lawson 2010).''' Reprinted with permission of Harold Lawson. All other rights are reserved by the copyright owner.]]
 
   
 
   
Figure 2 - Generic (T) Stage Structure of System Life Cycle Models
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Figure 5 shows the generic life cycle stages for a variety of stakeholders, from a standards organization (ISO/IEC) to commercial and government organizations. Although these stages differ in detail, they all have a similar sequential format that emphasizes the core activities as noted in Table 1 (concept, production, and utilization/retirement).   
(Lawson 2010, Figures 6-2 to 6-5)
 
  
The generic life cycle stages for a variety of different organizations, from standards (ISO/IEC) to commercial to government, are shown in Figure 3.  Note that although different in detail, all have a similar sequential format that emphasizes the core activities as noted in Figure 2.
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[[File:Comparisons_of_life_cycle_models.PNG|thumb|center|700px|'''Figure 5. Comparisons of Life Cycle Models (Forsberg, Mooz, and Cotterman 2005).''' Reprinted with permission of John Wiley & Sons. All other rights are reserved by the copyright owner.]]
  
[[File:Comparisons_of_life_cycle_models.PNG|600px|Comparisons of life cycle models (Forsberg, Mooz, and Cotterman 2005, p 87 updated)]]
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It is important to note that many of the activities throughout the life cycle are iterated. This is an example of recursion as discussed in the [[Systems Engineering and Management|Part 3 Introduction]].
  
Figure 3 - Comparisons of life cycle models (Forsberg, Mooz, and Cotterman 2005, p. 87 updated)
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==Fundamentals of Life Cycle Stages and Program Management Phase==
  
===Fundamentals of Life Cycle Stages and Program Management Phase===
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For this discussion, it is important to note that:
  
The notion of life cycle is related to the notion of program management that was presented in the previous section. Note that:
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*The term '''{{Term|Stage (glossary)|stage}}''' refers to the different states of a system during its life cycle; some stages may overlap in time, such as the utilization stage and the support stage. The term “stage” is used in [[ISO/IEC/IEEE 15288]].
  
* The term "stage" refers to the different states of the system during its life cycle; some stages may overlap in time such as the Utilization stage and the Support stage.  The term “stage” is used in [[ISO/IEC/IEEE 15288]].
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*The term '''phase''' refers to the different steps of the program that support and manage the life of the system; the phases usually do not overlap. The term “phase” is used in many well-established models as an equivalent to the term “stage.”
* The term "phase" refers to the different steps of the program that supports and manages the life of the system; the phases usually do not overlap. The term “Phase” is used in many well-established models as equivalent to “Stage.”
 
  
Program management employs phases, milestones, and decision gates during which the stages of the system evolve.   The stages contain the activities performed to achieve their goals; the phases serve to the control and the management of the sequence of stages and the transitions from one stage to the others. For each project it is essential that the team define and publish the terms and related definitions used on their project to minimize confusion.
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{{Term|Program Management (glossary)|Program management}} employs phases, {{Term|Milestone (glossary)|milestones}}, and {{Term|Decision Gate (glossary)|decision gates}} which are used to assess the evolution of a system through its various stages. The stages contain the activities performed to achieve goals and serve to control and manage the sequence of stages and the transitions between each stage. For each project, it is essential to define and publish the terms and related definitions used on respective projects to minimize confusion.
  
As an example, Figure 4 shows a typical program management sequence.    This classical program is composed of the following phases:
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A typical {{Term|Program (glossary)|program}} is composed of the following phases:
  
* '''The pre-study phase'''
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* The '''feasibility or study phase''' consists of studying the feasibility of alternative concepts to reach a second decision gate before initiating the execution stage. During the feasibility phase, stakeholders' requirements and system requirements are identified, viable solutions are identified and studied, and virtual {{Term|prototype (glossary)|prototypes (glossary)}} can be implemented. During this phase, the decision to move forward is based on:
* '''The feasibility phase''' - This phase consists of studying the feasibility of alternative concepts to reach a second decision gate before initiating the execution stage. It is the “go-ahead decision” based on:
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**whether a concept is feasible and is considered able to counter an identified threat or exploit an opportunity;
** Whether a concept is feasible and is considered able to counter an identified threat or exploit an opportunity.
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**whether a concept is sufficiently mature to warrant continued development of a new product or line of products; and
** Whether a concept is sufficiently mature to warrant continued development of a new product or line of products.
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**whether to approve a proposal generated in response to a request for proposal.
** Whether to approve a proposal generated in response to an RFP (Request for Proposal).
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*The '''execution phase''' includes activities related to four stages of the system life cycle: ''development, production, utilization, and support''. Typically, there are two decision gates and two milestones associated with execution activities. The first milestone provides the opportunity for management to review the plans for execution before giving the go-ahead. The second milestone provides the opportunity to review progress before the decision is made to initiate production. The decision gates during execution can be used to determine whether to produce the developed SoI and whether to improve it or retire it.
  
During the feasibility phase stakeholders' requirements and system requirements are identified, viable solutions are designed and studied, virtual [[prototype (glossary)|prototypes]] are engineered and can be implemented.
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These program management views apply not only to the SoI, but also to its elements and structure.
  
* '''The execution phase''' – This phase includes activities related to four stages of the system: development, production, utilization and support. Typically there are two decision gates and two milestones associated with execution activities. The first milestone provides the opportunity for management to review the plans for execution before giving the go-ahead. The second milestone provides the opportunity to review progress before the decision is made to initiate production. The decision gates during execution can be used to determine whether to produce the developed system-of-interest and whether to improve it or retire it.
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==Life Cycle Stages==
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Variations of the Vee model deal with the same general stages of a life cycle:
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*New projects typically begin with an exploratory research phase which generally includes the activities of [[System Concept Definition|system concept definition]], specifically the topics of [[Business or Mission Analysis|business or mission analysis]] and [[Stakeholder Needs Definition|stakeholder needs definition]] . These mature as the project goes from the exploratory stage to the concept stage to the development stage.
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*The production phase includes the activities of system definition and [[System Realization|system realization]], as well as the development of the system {{Term|System Requirement (glossary)|requirements (glossary)}} and {{Term|Architecture (glossary)|architecture (glossary)}} through [[System Verification|verification]] and [[System Validation|validation]].
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*The utilization phase includes the activities of [[System Deployment|system deployment]] and [[Operation of the System|system operation]].
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*The support phase includes the activities of [[System Maintenance|system maintenance]], [[logistics]], and [[Product and Service Life Management|product and service life management]], which may include activities such as [[Service Life Extension|service life extension]] or [[Capability Updates, Upgrades, and Modernization|capability updates, upgrades, and modernization]].
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*The retirement phase includes the activities of [[Disposal and Retirement|disposal and retirement]], though in some models, activities such as [[Service Life Extension|service life extension]] or [[Capability Updates, Upgrades, and Modernization|capability updates, upgrades, and modernization]] are grouped into the "retirement" phase.
  
These Program Management views apply not only to the system-of-interest but also to its elements and structure.
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Additional information on each of these stages can be found in the sections below (see links to additional Part 3 articles above for further detail). It is important to note that these life cycle stages, and the activities in each stage, are supported by a set of [[Systems Engineering Management|systems engineering management processes]].
  
[[File:KF_ProgramManagement&EngineeringViews.png|600px|Program Management and Engineering Views of the System Life Cycle]]
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===Concept Stage===
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[[Stakeholder Needs Definition|Stakeholder needs]] analysis and agreement is part of the concept stage and is critical to the development of successful systems. Without proper understanding of the user needs, any system runs the risk of being built to solve the wrong problems. The first step in the concept stage is to define the user (and stakeholder) requirements and constraints. A key part of this process is to establish the feasibility of meeting the user requirements, including technology readiness assessment. As with many SE activities this is often done iteratively, and stakeholder needs and requirements are revisited as new information becomes available.
Figure 4 - Program Management and Engineering Views of the sequential System Life Cycle
 
(ISO/IEC 19760:2003)
 
  
==Life Cycle Stages==
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A recent study by the National Research Council (National Research Council 2008) focused on reducing the development time for US Air Force projects. The report notes that, “simply stated, systems engineering is the translation of a user’s needs into a definition of a system and its architecture through an iterative process that results in an effective system design.” The iterative involvement with stakeholders is critical to the project success.
===Exploratory Research Stage===
 
 
 
The most important phase in the project cycle is the User Requirements Analysis and Agreement phase, which is part of the Exploratory Research Stage.  First,  define the user (and stakeholder) requirements and constraints.  
 
 
 
A key part of this process is to establish the feasibility of meeting the user requirements.
 
  
Except for the first and last Decision Gates of a project, the two Gates are performed simultaneously. See Figure 5.
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Except for the first and last decision gates of a project, the gates are performed simultaneously. See Figure 6 below.
 
   
 
   
[[File:KF_SchedulingDevelopment.png|600px|Scheduling the Development Phases]]
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[[File:KF_SchedulingDevelopment.png|800px|thumb|center|'''Figure 6. Scheduling the Development Phases.''' (SEBoK Original)]]During the [[System Concept Definition|concept stage]], alternate concepts are created to determine the best approach to meet stakeholder needs. By envisioning alternatives and creating models, including appropriate prototypes, stakeholder needs will be clarified and the driving issues highlighted. This may lead to an incremental or evolutionary approach to system development. Several different concepts may be explored in parallel.
  
Figure 5 - Scheduling the Development Phases (Faisandier 2010)
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===Development Stage ===
 
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The selected concept(s) identified in the concept stage are elaborated in detail down to the lowest level to produce the solution that meets the {{Term|Stakeholder Needs and Requirements (glossary)|stakeholder needs and requirements}}. Throughout this stage, it is vital to continue with user involvement through in-process validation (the upward arrow on the Vee models). On hardware, this is done with frequent program reviews and a customer resident representative(s) (if appropriate). In agile development, the practice is to have the customer representative integrated into the development team.
====Reviews====
 
 
 
To control the progress of a project different types of Reviews are planned.  The most commonly used are listed below but the names are not universal:
 
 
 
* System Requirements Review - SRR is planned to verify and validate the set of system requirements before starting the detailed design activities.
 
* Preliminary Design Review - PDR is planned to verify and validate the set of system requirements, the design artifacts and justification elements at the end of the first engineering loop.  This review is sometimes called the “Design-to” gate.
 
* Critical Design Review – CDR is planned to verify and validate the set of system requirements, the design artifacts and justification elements at the end of the last engineering loop. The “Build-to” and “Code-to” design is released after this review.
 
* [[Integration, Verification, and Validation (IV&V) (glossary)]] Reviews – As the components are assembled into higher level subsystems and elements, a sequence of reviews are held to ensure that everything integrates properly and that there is objective evidence that all requirements have been met (I&V).  There should also be an in-process validation that the system, as it is evolving, will meet the Stakeholders’ Requirements (see Figure 10).
 
* Final Validation Review – FVR is carried out at the end of the integration phase.
 
* Other Project Reviews related to management can be planned in order to control the correct progress of work, based on the type of system and associated risks.
 
 
 
 
 
[[File:KF_VeeModel_Right.png|600px|Right side of the Vee Model ]]
 
 
Figure 6 - Right side of the Vee Model (Forsberg, Mooz, and Cotterman 2005, Pg. 115)
 
  
 
===Production Stage===
 
===Production Stage===
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The production stage is where the SoI is built or manufactured. Product modifications may be required to resolve production problems, to reduce production costs, or to enhance product or SoI capabilities. Any of these modifications may influence system requirements and may require system re-{{Term|qualification (glossary)|qualification}}, re-{{Term|verification (glossary)|verification}}, or re-{{Term|validation (glossary)|validation}}. All such changes require SE assessment before changes are approved.
  
The Production Stage is where the system-of-interest is produced or manufactured.  Product modifications may be required to resolve production problems, to reduce production costs, or to enhance product or system-of-interest capabilities.  Any of these may influence system requirements and may require system re-[[qualification (glossary)|qualification]], re-[[verification (glossary)|verification]], or re-[[validation (glossary)|validation]]. All such changes require SE assessment before changes are approved.
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=== Utilization Stage===
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A significant aspect of product life cycle management is the provisioning of supporting systems which are vital in sustaining operation of the product. While the supplied product or service may be seen as the narrow system-of-interest (NSOI) for an {{Term|Acquirer (glossary)|acquirer}}, the acquirer also must incorporate the supporting systems into a wider system-of-interest (WSOI). These supporting systems should be seen as system assets that, when needed, are activated in response to a situation that has emerged in respect to the operation of the NSOI. The collective name for the set of supporting systems is the integrated logistics support (ILS) system.  
  
===Utilization Stage===
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It is vital to have a holistic view when defining, producing, and operating system products and services.  In Figure 7, the relationship between system design and development and the ILS requirements is portrayed.
  
A significant aspect of Product Life Cycle Management is the provisioning of supporting systems that are vital in sustaining operation of the product. While the supplied product or service may be seen as the NSOI (Narrow System of Interest) for an acquirer, the acquirer also must incorporate the supporting systems into a WSOI (Wider System of Interest).  These supporting systems should be seen as system assets that when needed are activated in responding to some situation that has arisen in respect to operation of the NSOI.  The collective name for the set of supporting systems is the Integrated Logistics Support (ILS) System. Some typical types of ILS supporting systems are indicated in Figure 7.
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[[File:KF_ILSSystemLifeCycle.png|frame|center|1100px|'''Figure 7. Relating ILS to the System Life Cycle (Eichmueller and Foreman 2009)'''Reprinted with permission of of ASD/AIA S3000L Steering Committee. All other rights are reserved by the copyright owner.]]
  
The ILS portrayed in the figure identifies several typical elements of this ILS system.  The elements are system assets for a supplying enterprise that are instantiated and put into operation in responding to logistics related situations.
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The requirements for reliability, resulting in the need of maintainability and testability, are driving factors.
  
As has been emphasized several times earlier, it is vital to have a holistic view when defining, producing and operating system products and services. In Figure 7 the relationship between system design and development and the ILS requirements is portrayed.
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===Support Stage===
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In the support stage, the SoI is provided services that enable continued operation.  Modifications may be proposed to resolve supportability problems, to reduce operational costs, or to extend the life of a system. These changes require SE assessment to avoid loss of system capabilities while under operation. The corresponding technical process is the maintenance process.
  
[[File:Typical_Integrated_Logistics_Support_(ILS)_Supporting_Systems.PNG|600px|Typical Integrated Logistics Support (ILS) Supporting Systems (Blanchard 2004)]]
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===Retirement Stage ===
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In the retirement stage, the SoI and its related services are removed from operation. SE activities in this stage are primarily focused on ensuring that disposal requirements are satisfied. In fact, planning for disposal is part of the system definition during the concept stage. Experiences in the 20th century repeatedly demonstrated the consequences when system retirement and disposal was not considered from the outset. Early in the 21st century, many countries have changed their laws to hold the creator of a SoI accountable for proper end-of-life disposal of the system.
  
Figure 7 - Typical Integrated Logistics Support (ILS) Supporting Systems (Blanchard 2004)
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==Life Cycle Reviews ==
  
[[File:KF_ILSSystemLifeCycle.png|600px|Relating ILS to the System Life Cycle]]
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To control the progress of a project, different types of reviews are planned. The most commonly used are listed as follows, although the names are not universal:
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*The '''system requirements review''' (SRR) is planned to verify and validate the set of system requirements before starting the detailed design activities.
Figure 8 - Relating ILS to the System Life Cycle  (ASD-STAN, Fig 1, 2009 Products and Services S3000L, www.asd-stn.org.)
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*The {{Term|Preliminary Design Review (PDR) (glossary)|preliminary design review}} (PDR) is planned to verify and validate the set of system requirements, the design artifacts, and justification elements at the end of the first engineering loop (also known as the "design-to" gate).
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* The {{Term|Critical Design Review (CDR) (glossary)|critical design review}} (CDR) is planned to verify and validate the set of system requirements, the design artifacts, and justification elements at the end of the last engineering loop (the “build-to” and “code-to” designs are released after this review).
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*The {{Term|integration (glossary)|integration}}, {{Term|verification (glossary)|verification}}, and {{Term|validation (glossary)|validation}} reviews are planned as the components are assembled into higher level subsystems and elements. A sequence of reviews is held to ensure that everything integrates properly and that there is objective evidence that all requirements have been met. There should also be an in-process validation that the system, as it is evolving, will meet the stakeholders’ requirements (see Figure 7).
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*The final validation review is carried out at the end of the integration phase.
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*Other management related reviews can be planned and conducted in order to control the correct progress of work, based on the type of system and the associated risks.
  
The requirements for reliability resulting in the need of maintainability and testability are driving factors.
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[[File:KF_VeeModel_Right.png|frame|center|400px|'''Figure 8. Right Side of the Vee Model (Forsberg, Mooz, and Cotterman 2005).''' Reprinted with permission of John Wiley & Sons Inc. All other rights are reserved by the copyright owner.]]
  
===Support Stage===
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==References==
  
In the Support Stage the system-of-interest is provided services that enable continued operation. Modifications may be proposed to resolve supportability problems, to reduce operational costs, or to extend the life of a system.  These changes require SE assessment to avoid loss of system capabilities while under operation.  The corresponding technical process is the Maintenance Process.
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=== Works Cited===
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Eichmueller, P. and B. Foreman. 2010. ''S3000LTM''. Brussels, Belgium: Aerospace and Defence Industries Association of Europe (ASD)/Aerospace Industries Association (AIA).
  
===Retirement Stage ===
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Faisandier, A. 2012. ''Systems Architecture and Design''. Belberaud, France: Sinergy'Com.
  
In the Retirement Stage the system-of-interest and its related services are removed from operation. SE activities in this stage are primarily focused on ensuring that disposal requirements are satisfied. In fact, planning for disposal is part of the system definition during the Concept Stage. Experience in the 20th century repeatedly demonstrated the consequences when system retirement and disposal are not considered from the outset. Early in the 21st century, many countries have changed their laws to hold the creator of a system-of-interest accountable for proper end-of-life disposal of the system.
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Forsberg, K., H. Mooz, and H. Cotterman. 2005. ''Visualizing Project Management,'' 3rd ed. New York, NY, USA: J. Wiley & Sons.
  
==References==
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INCOSE. 2012. ''Systems Engineering Handbook: A Guide for System Life Cycle Processes and Activities,'' 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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Lawson, H. 2010. ''A Journey Through the Systems Landscape.'' London, UK: College Publications, Kings College, UK.
  
===Citations===
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===Primary References===
Faisandier, A. 2011.[[ Engineering and Architecting Multidisciplinary Systems]] (to be published)..
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Beedle, M., et al. 2009. "[[The Agile Manifesto: Principles behind the Agile Manifesto]]". in ''The Agile Manifesto'' [database online]. Accessed December 04 2014 at www.agilemanifesto.org/principles.html
  
Forsberg, K., H. Mooz, H. Cotterman. 2005. [[Visualizing Project Management]]. 3rd Ed., J. Wiley & Sons.
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Boehm, B. and R. Turner. 2004. ''[[Balancing Agility and Discipline]].''  New York, NY, USA: Addison-Wesley.
  
INCOSE. 2011. [[INCOSE Systems Engineering Handbook|Systems Engineering Handbook]], version 3.2.1. INCOSE-TP-2003-002-03.2.1.
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Fairley, R. 2009. ''[[Managing and Leading Software Projects]].'' New York, NY, USA: J. Wiley & Sons.
  
Lawson, Harold. 2010. [[A Journey Through the Systems Landscape]], College Publications, Kings College, UK.
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Forsberg, K., H. Mooz, and H. Cotterman. 2005. ''[[Visualizing Project Management]].'' 3rd ed.  New York, NY, USA: J. Wiley & Sons.
  
===Primary References===
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INCOSE. 2012. ''[[INCOSE Systems Engineering Handbook|Systems Engineering Handbook]]: A Guide for System Life Cycle Processes and Activities'', version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE), INCOSE-TP-2003-002-03.2.2.
Boehm, B., J. Lane, S. Koolmanojwong, and R, Turner. 2012 (planned publication date). [[Embracing the Spiral Model]]: Creating Successful Systems with the Incremental Commitment Spiral Model. New York, NY, USA:Addison Wesley.
 
  
Boehm, B., and R. Turner. 2004. [[Balancing Agility and Discipline]]. New York, NY, USA: Addison-Wesley.
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Lawson, H. 2010. ''[[A Journey Through the Systems Landscape]].'' Kings College, UK: College Publications.
  
Fairley, R. 2009. [[Managing and Leading Software Projects]]. New York, NY, USA: J. Wiley & Sons.
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Pew, R., and A. Mavor (eds.) 2007. ''[[Human-System Integration in the System Development Process]]: A New Look.'' Washington, DC, USA: The National Academies Press.
  
Forsberg, K., H. Mooz, H. Cotterman. 2005.[[ Visualizing Project Management]]. 3rd Ed.  New York, NY, USA: J. Wiley & Sons.
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Royce, W.E. 1998. ''[[Software Project Management]]: A Unified Framework''. New York, NY, USA: Addison Wesley.
  
Faisandier, A2011. [[Engineering and Architecting Multidisciplinary Systems]] (to be published).
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===Additional References===
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Anderson, D. 2010. ''Kanban''Sequim, WA, USA: Blue Hole Press.
  
INCOSE. 2011. [[INCOSE Systems Engineering Handbook|Systems Engineering Handbook]], version 3.2.1. INCOSE-TP-2003-002-03.2.1.
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Baldwin, C. and K. Clark. 2000. ''Design Rules: The Power of Modularity.'' Cambridge, MA, USA: MIT Press.  
  
Lawson, Harold. 2010. [[A Journey Through the Systems Landscape]]. London, UK: College Publications.
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Beck, K. 1999. ''Extreme Programming Explained.'' New York, NY, USA: Addison Wesley.  
  
Pew, R., and A. Mavor (eds.) 2007. [[Human-System Integration in the System Development Process]]: A New Look. Washington, D.C., USA: The National Academies Press. http://www.nap.edu
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Beedle, M., et al. 2009. "The Agile Manifesto: Principles behind the Agile Manifesto". in The Agile Manifesto [database online]. Accessed 2010. Available at: www.agilemanifesto.org/principles.html
  
“Principles behind the Agile Manifesto,” 15 Dec 2009, http://www.agilemanifesto.org/principles.html
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Biffl, S., A. Aurum, B. Boehm, H. Erdogmus, and P. Gruenbacher (eds.). 2005. ''Value-Based Software Engineering''. New York, NY, USA: Springer.
  
Royce, W. E. 1998. ''Software Project Management''. New York, NY, USA: Addison Wesley.
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Boehm, B. 1988. “A Spiral Model of Software Development.” IEEE ''Computer'' 21(5): 61-72.
  
===Additional References===
+
Boehm, B. 2006. “Some Future Trends and Implications for Systems and Software Engineering Processes.''Systems Engineering.'' 9(1): 1-19.
Anderson, D., 2010. ''Kanban''.  Sequim, WA, USA: Blue Hole Press.
 
  
Baldwin, C., and K. Clark, 2000. ''Design Rules: The Power of Modularity.'' Cambridge, MA, USA: MIT Press.  
+
Boehm, B., A. Egyed, J. Kwan, D. Port, A. Shah, and R. Madachy. 1998. “Using the WinWin Spiral Model: A Case Study.” IEEE ''Computer.'' 31(7): 33-44.
  
Beck, K., 1999. ''Extreme Programming Explained.'' New York, NY, USA: Addison Wesley.  
+
Boehm, B., R. Turner, J. Lane, S. Koolmanojwong. 2014 (in press). ''Embracing the Spiral Model: Creating Successful Systems with the Incremental Commitment Spiral Model''. Boston, MA, USA: Addison Wesley.
  
Biffl, S.,  A. Aurum, B. Boehm, H. Erdogmus, P. Gruenbacher (eds.), 2005. ''Value-Based Software Engineering''. New York, NY, USA: Springer.
+
Castellano, D.R. 2004. “Top Five Quality Software Projects.” ''CrossTalk.'' 17(7) (July 2004): 4-19. Available at: http://www.crosstalkonline.org/storage/issue-archives/2004/200407/200407-0-Issue.pdf
  
Boehm, B., May 1988. “A Spiral Model of Software Development,” ''Computer'' 21(5), pp. 61-72.
+
Checkland, P. 1981. ''Systems Thinking, Systems Practice''. New York, NY, USA: Wiley.
  
Boehm, B., 2006. “Some Future Trends and Implications for Systems and Software Engineering Processes”, ''Systems Engineering'' 9(1), pp. 1-19.
+
Crosson, S. and B. Boehm. 2009. “Adjusting Software Life cycle Anchorpoints: Lessons Learned in a System of Systems Context.” Proceedings of the Systems and Software Technology Conference, 20-23 April 2009, Salt Lake City, UT, USA.
 +
 +
Dingsoyr, T., T. Dyba. and N. Moe (eds.). 2010. "Agile Software Development: Current Research and Future Directions.”  Chapter in B. Boehm, J. Lane, S. Koolmanjwong, and R. Turner, ''Architected Agile Solutions for Software-Reliant Systems.'' New York, NY, USA: Springer.
  
Boehm, B., A. Egyed, J. Kwan, D. Port, A. Shah, and R. Madachy, July 1998. “Using the WinWin Spiral Model: A Case Study,” ''IEEE Computer'', 31(7): 33-44.
+
Dorner, D. 1996. ''The Logic of Failure''.  New York, NY, USA: Basic Books.
  
Checkland, P., 1981. ''Systems Thinking, Systems Practice''. New York, NY, USA: Wiley.
+
Forsberg, K. 1995. "'If I Could Do That, Then I Could…' System Engineering in a Research and Development Environment.” Proceedings of the Fifth Annual International Council on Systems Engineering (INCOSE) International Symposium. 22-26 July 1995. St. Louis, MO, USA.
  
CrossTalk, January 2002, July 2003, July 2004, September 2005. “Top Five Quality Software Projects,” www.stsc.hill.af.mil/crosstalk
+
Forsberg, K. 2010. “Projects Don’t Begin With Requirements.” Proceedings of the IEEE Systems Conference, 5-8 April 2010, San Diego, CA, USA.
 
Crosson, S., and B. Boehm, April 2009. “Adjusting Software Life cycle Anchorpoints: Lessons Learned in a System of Systems Context,” Proceedings, SSTC 2009.
 
 
Dingsoyr, T., T. Dyba. and N. Moe (eds.). 2010 "Agile Software Development: Current Research and Future Directions”; Chapter in  Boehm, J. Lane, S. Koolmanjwong, and R, Turner, ''Architected Agile Solutions for Software-Reliant Systems.'' New York, NY, USA: Springer.
 
  
Dorner, D., 1996. ''The Logic of Failure''.  New York, NY, USA: Basic Books.
+
Gilb, T. 2005. ''Competitive Engineering''.  Maryland Heights, MO, USA: Elsevier Butterworth Heinemann.
  
Forsberg, K. 1995. “’If I Could Do That, Then I Could…’ System Engineering in a Research and Development Environment,” Proceedings,   Fifth INCOSE Summer Symposium.
+
Goldratt, E. 1984. ''The Goal''. Great Barrington, MA, USA: North River Press.
  
Forsberg, K. 2010. “Projects Don’t Begin With Requirements.” IEEE Systems Conf. San Diego, CA. April.
+
Hitchins, D. 2007. ''Systems Engineering: A 21st Century Systems Methodology.''  New York, NY, USA: Wiley.
  
Gilb, T., 2005. ''Competitive Engineering''. Maryland Heights, MO, USA: Elsevier Butterworth Heinemann.
+
Holland, J. 1998. ''Emergence''. New York, NY, USA: Perseus Books.
  
Goldratt, E., 1984. ''The Goal''Great Barrington, MA, USA: North River Press.
+
ISO/IEC. 2010. Systems and Software Engineering, Part 1: Guide for Life Cycle ManagementGeneva, Switzerland: International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC), ISO/IEC 24748-1:2010.  
  
Hitchins, D.,  2007. ''Systems Engineering: A 21st Century Systems Methodology''. New York, NY, USA: Wiley.
+
ISO/IEC/IEEE. 2015. ''Systems and Software Engineering -- System Life Cycle Processes.'' Geneva, Switzerland: International Organisation for Standardisation / International Electrotechnical Commissions / Institute of Electrical and Electronics Engineers. ISO/IEC/IEEE 15288:2015.
  
Holland, J., 1998. ''Emergence''. New York, NY, USA: Perseus Books.
+
ISO/IEC. 2003. ''Systems Engineering — A Guide for The Application of ISO/IEC 15288 System Life Cycle Processes''. Geneva, Switzerland: International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC), ISO/IEC 19760:2003 (E).
  
ISO/IEC 15288:2008. Systems and software engineering – System life cycle processes.
+
Jarzombek, J. 2003. “Top Five Quality Software Projects.” ''CrossTalk.'' 16(7) (July 2003): 4-19. Available at: http://www.crosstalkonline.org/storage/issue-archives/2003/200307/200307-0-Issue.pdf.
  
ISO/IEC 19760:2003. A guide for application of ISO/IEC 15288 System Life Cycle Processes.
+
Kruchten, P. 1999. ''The Rational Unified Process.'' New York, NY, USA: Addison Wesley.
  
ISO/IEC 24748-1:2010Systems and software engineering, Part 1: Guide for life cycle management
+
Landis, T. R. 2010. ''Lockheed Blackbird Family (A-12, YF-12, D-21/M-21 & SR-71).'' North Branch, MN, USA: Specialty Press.
  
Kruchten, P., 1999. ''The Rational Unified Process''. New York, NY, USA: Addison Wesley.
+
Madachy, R. 2008. ''Software Process Dynamics''. Hoboken, NJ, USA: Wiley.
  
Landis, T. R. 2010. ''Lockheed Blackbird Family (A-12, YF-12, D-21/M-21 & SR-71)''. North Branch, MN, USA: Specialty Press.
+
Maranzano, J.F., S.A. Rozsypal, G.H. Zimmerman, G.W. Warnken, P.E. Wirth, D.W. Weiss. 2005. “Architecture Reviews: Practice and Experience.” IEEE ''Software.'' 22(2): 34-43.
  
Madachy, R., 2008. ''Software Process Dynamics''. New York, NY, USA: Wiley.
+
National Research Council of the National Academies (USA). 2008. ''Pre-Milestone A and Early-Phase Systems Engineering''. Washington, DC, USA: The National Academies Press.  
  
Maranzano, J., et al., March/April 2005, “Architecture reviews: Practice and experience,” ''IEEE Software'', pp. 34-43.
+
Osterweil, L. 1987. “Software Processes are Software Too.” Proceedings of the SEFM 2011: 9th International Conference on Software Engineering. Monterey, CA, USA.
  
National Research Council of the National Academies (USA). 2008. ''Pre-Milestone A and Early-Phase Systems Engineering''.  Washington, D.C., USA: The National Academies Press. http://www.nap.edu
+
Poppendeick, M. and T. Poppendeick. 2003. ''Lean Software Development: an Agile Toolkit.'' New York, NY, USA: Addison Wesley.
  
Osterweil, L. 1987. “Software Processes are Software Too,” Proceedings, ICSE 9.
+
Rechtin, E. 1991. ''System Architecting: Creating and Building Complex Systems.'' Upper Saddle River, NY, USA: Prentice-Hall.
  
Poppendeick, M. and T., 2003. ''Lean Software Development: an Agile Toolkit''. New York, NY, USA: Addison Wesley.
+
Rechtin, E., and M. Maier. 1997. ''The Art of System Architecting''. Boca Raton, FL, USA: CRC Press.  
  
“Principles behind the Agile Manifesto,” 15 Dec 2009, http://www.agilemanifesto.org/principles.html
+
Schwaber, K. and M. Beedle. 2002. ''Agile Software Development with Scrum''. Upper Saddle River, NY, USA: Prentice Hall.  
  
Rechtin, E. 1991. ''System Architecting.: Creating and Building Complex Systems''. Upper Saddle River, NY, USA: Prentice-Hall.
+
Spruill, N. 2002. “Top Five Quality Software Projects.” ''CrossTalk.'' 15(1) (January 2002): 4-19. Available at: http://www.crosstalkonline.org/storage/issue-archives/2002/200201/200201-0-Issue.pdf.
  
Rechtin, E., and M. Maier, 1997. ''The Art of System Architecting''. Boca Raton, FL, USA: CRC Press.  
+
Stauder, T. 2005. “Top Five Department of Defense Program Awards.''CrossTalk.'' 18(9) (September 2005): 4-13. Available at http://www.crosstalkonline.org/storage/issue-archives/2005/200509/200509-0-Issue.pdf.
  
Schwaber, K. and M. Beedle, 2002. ''Agile Software Development with Scrum''.   Upper Saddle River, NY, USA:Prentice Hall.  
+
Warfield, J. 1976. ''Societal Systems: Planning, Policy, and Complexity''. New York, NY, USA: Wiley.
  
Warfield, J., 1976. ''Societal Systems: Planning, Policy, and Complexity''New York, NY, USA: Wiley.
+
Womack, J. and D. Jones. 1996. ''Lean Thinking.'' New York, NY, USA: Simon and Schuster.
  
Womack, J., and D. Jones, 1996. ''Lean Thinking''. New York, NY, USA: Simon and Schuster.
+
=== Relevant Videos ===
 +
*[https://www.youtube.com/watch?v=9b4GYQfUuGE&t=7s Basic Introduction of Systems Engineering (V-method) [Part 1 of 2]]
 +
*[https://www.youtube.com/watch?v=q8vJogfrAnE Basic Introduction to Systems Engineering (V-Method) Part 2 of 2]
 
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====Article Discussion====
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<center>[[System Life Cycle Process Drivers and Choices|< Previous Article]]  |  [[System Life Cycle Models|Parent Article]]  |  [[Incremental Life Cycle Model|Next Article >]] </center>
  
[[{{TALKPAGENAME}}|[Go to discussion page]]]
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<center>'''SEBoK v. 2.10, released 06 May 2024'''</center>
<center>[[System Life Cycle Process Drivers and Choices|<- Previous Article]] | [[Life Cycle Models|Parent Article]] | [[System Life Cycle Process Models: Iterative|Next Article ->]]</center>
 
  
==Signatures==
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[[Category: Part 3]]
[[Category: Part 3]][[Category:Topic]]
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[[Category:Topic]]
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[[Category:Life Cycle Models]]

Latest revision as of 23:02, 2 May 2024


Lead Authors: Dick Fairley, Kevin Forsberg, Contributing Author: Ray Madachy, Phyllis Marbach


There are a large number of life cycle process models. As discussed in the System Life Cycle Process Drivers and Choices article, those models described fall into three major categories: (1) primarily pre-specified single-step or multistep, also known as traditional or sequential processes; (2) evolutionary sequential (or the Vee Model) and (3) evolutionary opportunistic and evolutionary concurrent (or incremental agile). The concurrent processes are known by many names: the agile unified process (formerly the Rational Unified Process), the spiral models) and include some that are primarily interpersonal and unconstrained processes (e.g., agile development, Scrum, extreme programming (XP), the dynamic system development method, and innovation-based processes).

This article specifically focuses on the Vee Model as the primary example of pre-specified and sequential processes. In this discussion, it is important to note that the Vee model, and variations of the Vee model, all address the same basic set of systems engineering (SE) activities. The key difference between these models is the way in which they group and represent the aforementioned SE activities.

General implications of using the Vee model for system design and development are discussed below; for a more specific understanding of how this life cycle model impacts systems engineering activities, please see the other knowledge areas (KAs) in Part 3.

A Primarily Pre-specified and Sequential Process Model: The Vee Model

The sequential version of the Vee Model is shown in Figure 1. Its core involves a sequential progression of plans, specifications, and products that are baselined and put under configuration management. The vertical, two-headed arrow enables projects to perform concurrent opportunity and risk analyses, as well as continuous in-process validation. The Vee Model encompasses the first two life cycle stages listed in the "Generic Life Cycle Stages their purposes, and decision gate options" table of the INCOSE Systems Engineering Handbook: concept, and development (INCOSE 2015).

Figure 1. Left Side of the Sequential Vee Model (INCOSE 2015, adapted from Forsberg, Mooz, and Cotterman 2005, Reprinted with permission of John Wiley & Sons Inc. All other rights are reserved by the copyright owner.

The Vee Model endorses the INCOSE Systems Engineering Handbook (INCOSE 2015) definition of life cycle stages and their purposes or activities, as shown in Figure 2 below. Replace Figure 2 with the updated figure that removes the first Exploratory stage.

Figure 2. An Example of Stages, Their Purposes and Major Decision Gates. (SEBoK Original)

A more detailed version of the Vee diagram incorporates life cycle activities into the more generic Vee model. This Vee diagram, developed at the U.S. Defense Acquisition University (DAU), can be seen in Figure 3 below.

Figure 3. The Vee Activity Diagram (Prosnik 2010). Released by the Defense Acquisition University (DAU)/U.S. Department of Defense (DoD).

Application of the Vee Model

Lawson (Lawson 2010) elaborates on the activities in each life cycle stage and notes that it is useful to consider the structure of a generic life cycle stage model for any type of system-of-interest (SoI) as portrayed in Figure 4. This (T) model indicates that one or more definition stages precede a production stage(s) where the implementation (acquisition, provisioning, or development) of two or more system elements has been accomplished.

Figure 4. Generic (T) Stage Structure of System Life Cycle Models (Lawson 2010). Reprinted with permission of Harold Lawson. All other rights are reserved by the copyright owner.

Figure 5 shows the generic life cycle stages for a variety of stakeholders, from a standards organization (ISO/IEC) to commercial and government organizations. Although these stages differ in detail, they all have a similar sequential format that emphasizes the core activities as noted in Table 1 (concept, production, and utilization/retirement).

Figure 5. Comparisons of Life Cycle Models (Forsberg, Mooz, and Cotterman 2005). Reprinted with permission of John Wiley & Sons. All other rights are reserved by the copyright owner.

It is important to note that many of the activities throughout the life cycle are iterated. This is an example of recursion as discussed in the Part 3 Introduction.

Fundamentals of Life Cycle Stages and Program Management Phase

For this discussion, it is important to note that:

  • The term stagestage refers to the different states of a system during its life cycle; some stages may overlap in time, such as the utilization stage and the support stage. The term “stage” is used in ISO/IEC/IEEE 15288.
  • The term phase refers to the different steps of the program that support and manage the life of the system; the phases usually do not overlap. The term “phase” is used in many well-established models as an equivalent to the term “stage.”

Program managementProgram management employs phases, milestonesmilestones, and decision gatesdecision gates which are used to assess the evolution of a system through its various stages. The stages contain the activities performed to achieve goals and serve to control and manage the sequence of stages and the transitions between each stage. For each project, it is essential to define and publish the terms and related definitions used on respective projects to minimize confusion.

A typical programprogram is composed of the following phases:

  • The feasibility or study phase consists of studying the feasibility of alternative concepts to reach a second decision gate before initiating the execution stage. During the feasibility phase, stakeholders' requirements and system requirements are identified, viable solutions are identified and studied, and virtual prototypes (glossary)prototypes (glossary) can be implemented. During this phase, the decision to move forward is based on:
    • whether a concept is feasible and is considered able to counter an identified threat or exploit an opportunity;
    • whether a concept is sufficiently mature to warrant continued development of a new product or line of products; and
    • whether to approve a proposal generated in response to a request for proposal.
  • The execution phase includes activities related to four stages of the system life cycle: development, production, utilization, and support. Typically, there are two decision gates and two milestones associated with execution activities. The first milestone provides the opportunity for management to review the plans for execution before giving the go-ahead. The second milestone provides the opportunity to review progress before the decision is made to initiate production. The decision gates during execution can be used to determine whether to produce the developed SoI and whether to improve it or retire it.

These program management views apply not only to the SoI, but also to its elements and structure.

Life Cycle Stages

Variations of the Vee model deal with the same general stages of a life cycle:

Additional information on each of these stages can be found in the sections below (see links to additional Part 3 articles above for further detail). It is important to note that these life cycle stages, and the activities in each stage, are supported by a set of systems engineering management processes.

Concept Stage

Stakeholder needs analysis and agreement is part of the concept stage and is critical to the development of successful systems. Without proper understanding of the user needs, any system runs the risk of being built to solve the wrong problems. The first step in the concept stage is to define the user (and stakeholder) requirements and constraints. A key part of this process is to establish the feasibility of meeting the user requirements, including technology readiness assessment. As with many SE activities this is often done iteratively, and stakeholder needs and requirements are revisited as new information becomes available.

A recent study by the National Research Council (National Research Council 2008) focused on reducing the development time for US Air Force projects. The report notes that, “simply stated, systems engineering is the translation of a user’s needs into a definition of a system and its architecture through an iterative process that results in an effective system design.” The iterative involvement with stakeholders is critical to the project success.

Except for the first and last decision gates of a project, the gates are performed simultaneously. See Figure 6 below.

Figure 6. Scheduling the Development Phases. (SEBoK Original)

During the concept stage, alternate concepts are created to determine the best approach to meet stakeholder needs. By envisioning alternatives and creating models, including appropriate prototypes, stakeholder needs will be clarified and the driving issues highlighted. This may lead to an incremental or evolutionary approach to system development. Several different concepts may be explored in parallel.

Development Stage

The selected concept(s) identified in the concept stage are elaborated in detail down to the lowest level to produce the solution that meets the stakeholder needs and requirementsstakeholder needs and requirements. Throughout this stage, it is vital to continue with user involvement through in-process validation (the upward arrow on the Vee models). On hardware, this is done with frequent program reviews and a customer resident representative(s) (if appropriate). In agile development, the practice is to have the customer representative integrated into the development team.

Production Stage

The production stage is where the SoI is built or manufactured. Product modifications may be required to resolve production problems, to reduce production costs, or to enhance product or SoI capabilities. Any of these modifications may influence system requirements and may require system re-qualificationqualification, re-verificationverification, or re-validationvalidation. All such changes require SE assessment before changes are approved.

Utilization Stage

A significant aspect of product life cycle management is the provisioning of supporting systems which are vital in sustaining operation of the product. While the supplied product or service may be seen as the narrow system-of-interest (NSOI) for an acquireracquirer, the acquirer also must incorporate the supporting systems into a wider system-of-interest (WSOI). These supporting systems should be seen as system assets that, when needed, are activated in response to a situation that has emerged in respect to the operation of the NSOI. The collective name for the set of supporting systems is the integrated logistics support (ILS) system.

It is vital to have a holistic view when defining, producing, and operating system products and services. In Figure 7, the relationship between system design and development and the ILS requirements is portrayed.

Figure 7. Relating ILS to the System Life Cycle (Eichmueller and Foreman 2009). Reprinted with permission of of ASD/AIA S3000L Steering Committee. All other rights are reserved by the copyright owner.

The requirements for reliability, resulting in the need of maintainability and testability, are driving factors.

Support Stage

In the support stage, the SoI is provided services that enable continued operation. Modifications may be proposed to resolve supportability problems, to reduce operational costs, or to extend the life of a system. These changes require SE assessment to avoid loss of system capabilities while under operation. The corresponding technical process is the maintenance process.

Retirement Stage

In the retirement stage, the SoI and its related services are removed from operation. SE activities in this stage are primarily focused on ensuring that disposal requirements are satisfied. In fact, planning for disposal is part of the system definition during the concept stage. Experiences in the 20th century repeatedly demonstrated the consequences when system retirement and disposal was not considered from the outset. Early in the 21st century, many countries have changed their laws to hold the creator of a SoI accountable for proper end-of-life disposal of the system.

Life Cycle Reviews

To control the progress of a project, different types of reviews are planned. The most commonly used are listed as follows, although the names are not universal:

  • The system requirements review (SRR) is planned to verify and validate the set of system requirements before starting the detailed design activities.
  • The preliminary design reviewpreliminary design review (PDR) is planned to verify and validate the set of system requirements, the design artifacts, and justification elements at the end of the first engineering loop (also known as the "design-to" gate).
  • The critical design reviewcritical design review (CDR) is planned to verify and validate the set of system requirements, the design artifacts, and justification elements at the end of the last engineering loop (the “build-to” and “code-to” designs are released after this review).
  • The integrationintegration, verificationverification, and validationvalidation reviews are planned as the components are assembled into higher level subsystems and elements. A sequence of reviews is held to ensure that everything integrates properly and that there is objective evidence that all requirements have been met. There should also be an in-process validation that the system, as it is evolving, will meet the stakeholders’ requirements (see Figure 7).
  • The final validation review is carried out at the end of the integration phase.
  • Other management related reviews can be planned and conducted in order to control the correct progress of work, based on the type of system and the associated risks.
Figure 8. Right Side of the Vee Model (Forsberg, Mooz, and Cotterman 2005). Reprinted with permission of John Wiley & Sons Inc. All other rights are reserved by the copyright owner.

References

Works Cited

Eichmueller, P. and B. Foreman. 2010. S3000LTM. Brussels, Belgium: Aerospace and Defence Industries Association of Europe (ASD)/Aerospace Industries Association (AIA).

Faisandier, A. 2012. Systems Architecture and Design. Belberaud, France: Sinergy'Com.

Forsberg, K., H. Mooz, and H. Cotterman. 2005. Visualizing Project Management, 3rd ed. New York, NY, USA: J. Wiley & Sons.

INCOSE. 2012. Systems Engineering Handbook: A Guide for System Life Cycle Processes and Activities, version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE), INCOSE-TP-2003-002-03.2.2.

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

Primary References

Beedle, M., et al. 2009. "The Agile Manifesto: Principles behind the Agile Manifesto". in The Agile Manifesto [database online]. Accessed December 04 2014 at www.agilemanifesto.org/principles.html

Boehm, B. and R. Turner. 2004. Balancing Agility and Discipline. New York, NY, USA: Addison-Wesley.

Fairley, R. 2009. Managing and Leading Software Projects. New York, NY, USA: J. Wiley & Sons.

Forsberg, K., H. Mooz, and H. Cotterman. 2005. Visualizing Project Management. 3rd ed. New York, NY, USA: J. Wiley & Sons.

INCOSE. 2012. Systems Engineering Handbook: A Guide for System Life Cycle Processes and Activities, version 3.2.2. San Diego, CA, USA: International Council on Systems Engineering (INCOSE), INCOSE-TP-2003-002-03.2.2.

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

Pew, R., and A. Mavor (eds.) 2007. Human-System Integration in the System Development Process: A New Look. Washington, DC, USA: The National Academies Press.

Royce, W.E. 1998. Software Project Management: A Unified Framework. New York, NY, USA: Addison Wesley.

Additional References

Anderson, D. 2010. Kanban. Sequim, WA, USA: Blue Hole Press.

Baldwin, C. and K. Clark. 2000. Design Rules: The Power of Modularity. Cambridge, MA, USA: MIT Press.

Beck, K. 1999. Extreme Programming Explained. New York, NY, USA: Addison Wesley.

Beedle, M., et al. 2009. "The Agile Manifesto: Principles behind the Agile Manifesto". in The Agile Manifesto [database online]. Accessed 2010. Available at: www.agilemanifesto.org/principles.html

Biffl, S., A. Aurum, B. Boehm, H. Erdogmus, and P. Gruenbacher (eds.). 2005. Value-Based Software Engineering. New York, NY, USA: Springer.

Boehm, B. 1988. “A Spiral Model of Software Development.” IEEE Computer 21(5): 61-72.

Boehm, B. 2006. “Some Future Trends and Implications for Systems and Software Engineering Processes.” Systems Engineering. 9(1): 1-19.

Boehm, B., A. Egyed, J. Kwan, D. Port, A. Shah, and R. Madachy. 1998. “Using the WinWin Spiral Model: A Case Study.” IEEE Computer. 31(7): 33-44.

Boehm, B., R. Turner, J. Lane, S. Koolmanojwong. 2014 (in press). Embracing the Spiral Model: Creating Successful Systems with the Incremental Commitment Spiral Model. Boston, MA, USA: Addison Wesley.

Castellano, D.R. 2004. “Top Five Quality Software Projects.” CrossTalk. 17(7) (July 2004): 4-19. Available at: http://www.crosstalkonline.org/storage/issue-archives/2004/200407/200407-0-Issue.pdf

Checkland, P. 1981. Systems Thinking, Systems Practice. New York, NY, USA: Wiley.

Crosson, S. and B. Boehm. 2009. “Adjusting Software Life cycle Anchorpoints: Lessons Learned in a System of Systems Context.” Proceedings of the Systems and Software Technology Conference, 20-23 April 2009, Salt Lake City, UT, USA.

Dingsoyr, T., T. Dyba. and N. Moe (eds.). 2010. "Agile Software Development: Current Research and Future Directions.” Chapter in B. Boehm, J. Lane, S. Koolmanjwong, and R. Turner, Architected Agile Solutions for Software-Reliant Systems. New York, NY, USA: Springer.

Dorner, D. 1996. The Logic of Failure. New York, NY, USA: Basic Books.

Forsberg, K. 1995. "'If I Could Do That, Then I Could…' System Engineering in a Research and Development Environment.” Proceedings of the Fifth Annual International Council on Systems Engineering (INCOSE) International Symposium. 22-26 July 1995. St. Louis, MO, USA.

Forsberg, K. 2010. “Projects Don’t Begin With Requirements.” Proceedings of the IEEE Systems Conference, 5-8 April 2010, San Diego, CA, USA.

Gilb, T. 2005. Competitive Engineering. Maryland Heights, MO, USA: Elsevier Butterworth Heinemann.

Goldratt, E. 1984. The Goal. Great Barrington, MA, USA: North River Press.

Hitchins, D. 2007. Systems Engineering: A 21st Century Systems Methodology. New York, NY, USA: Wiley.

Holland, J. 1998. Emergence. New York, NY, USA: Perseus Books.

ISO/IEC. 2010. Systems and Software Engineering, Part 1: Guide for Life Cycle Management. Geneva, Switzerland: International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC), ISO/IEC 24748-1:2010.

ISO/IEC/IEEE. 2015. Systems and Software Engineering -- System Life Cycle Processes. Geneva, Switzerland: International Organisation for Standardisation / International Electrotechnical Commissions / Institute of Electrical and Electronics Engineers. ISO/IEC/IEEE 15288:2015.

ISO/IEC. 2003. Systems Engineering — A Guide for The Application of ISO/IEC 15288 System Life Cycle Processes. Geneva, Switzerland: International Organization for Standardization (ISO)/International Electrotechnical Commission (IEC), ISO/IEC 19760:2003 (E).

Jarzombek, J. 2003. “Top Five Quality Software Projects.” CrossTalk. 16(7) (July 2003): 4-19. Available at: http://www.crosstalkonline.org/storage/issue-archives/2003/200307/200307-0-Issue.pdf.

Kruchten, P. 1999. The Rational Unified Process. New York, NY, USA: Addison Wesley.

Landis, T. R. 2010. Lockheed Blackbird Family (A-12, YF-12, D-21/M-21 & SR-71). North Branch, MN, USA: Specialty Press.

Madachy, R. 2008. Software Process Dynamics. Hoboken, NJ, USA: Wiley.

Maranzano, J.F., S.A. Rozsypal, G.H. Zimmerman, G.W. Warnken, P.E. Wirth, D.W. Weiss. 2005. “Architecture Reviews: Practice and Experience.” IEEE Software. 22(2): 34-43.

National Research Council of the National Academies (USA). 2008. Pre-Milestone A and Early-Phase Systems Engineering. Washington, DC, USA: The National Academies Press.

Osterweil, L. 1987. “Software Processes are Software Too.” Proceedings of the SEFM 2011: 9th International Conference on Software Engineering. Monterey, CA, USA.

Poppendeick, M. and T. Poppendeick. 2003. Lean Software Development: an Agile Toolkit. New York, NY, USA: Addison Wesley.

Rechtin, E. 1991. System Architecting: Creating and Building Complex Systems. Upper Saddle River, NY, USA: Prentice-Hall.

Rechtin, E., and M. Maier. 1997. The Art of System Architecting. Boca Raton, FL, USA: CRC Press.

Schwaber, K. and M. Beedle. 2002. Agile Software Development with Scrum. Upper Saddle River, NY, USA: Prentice Hall.

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