Difference between revisions of "Generic Life Cycle Model"
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Figure 1 shows just the single-step approach for proceeding through the stages of a system’s life cycle. In [[Life Cycle Models]] knowledge area we discuss examples of real world enterprises and their drivers, both technical and organizational. These have lead to a number of documented approaches for sequencing the life cycle stages to deal with some of the issues raised. The Life Cycle Models KA summarizes a number of [[Incremental (glossary)|incremental]] and [[Evolutionary (glossary)|evolutionary]] life cycle models, including their main strengths and weaknesses and also discusses criteria for choosing the best-fit approach. | Figure 1 shows just the single-step approach for proceeding through the stages of a system’s life cycle. In [[Life Cycle Models]] knowledge area we discuss examples of real world enterprises and their drivers, both technical and organizational. These have lead to a number of documented approaches for sequencing the life cycle stages to deal with some of the issues raised. The Life Cycle Models KA summarizes a number of [[Incremental (glossary)|incremental]] and [[Evolutionary (glossary)|evolutionary]] life cycle models, including their main strengths and weaknesses and also discusses criteria for choosing the best-fit approach. | ||
| − | In figure 1 we have listed key aechnical and management ctivities critical to successful completion of each stage. This is a useful way to illustrate the goals of each stage and gives an indication of how processes align with these stages. This can be important when considering how to plan for resources, milestones, etc. However, it is important to observe that the execution of process activities are not compartmentalized to particular life cycle stages (Lawson 2010). In [[Applying Life Cycle Processes]] we discuss a number of views on the nature of the inter-relationships between process activities within a life cycle model. In general, the technical and management activities are applied in accordance with the principles of [[Concurrent (glossary)]], [[Iteration (glossary)]] and [[Recursion (glossary]] described in the [[Introduction to Life Cycle Processes (glossary| generic life cycle paradigm]]. | + | In figure 1 we have listed key aechnical and management ctivities critical to successful completion of each stage. This is a useful way to illustrate the goals of each stage and gives an indication of how processes align with these stages. This can be important when considering how to plan for resources, milestones, etc. However, it is important to observe that the execution of process activities are not compartmentalized to particular life cycle stages (Lawson 2010). In [[Applying Life Cycle Processes]] we discuss a number of views on the nature of the inter-relationships between process activities within a life cycle model. In general, the technical and management activities are applied in accordance with the principles of [[Concurrent (glossary)]], [[Iteration (glossary)]] and [[Recursion (glossary)]] described in the [[Introduction to Life Cycle Processes (glossary| generic life cycle paradigm]]. |
==References== | ==References== | ||
Revision as of 08:19, 15 May 2015
As discussed in the generic life cycle paradigm in Introduction to Life Cycle Processes each system-of-interest has an associated life cycle model . The generic life cycle model below applies to a single SoI. SE must generally be synchronised across a number of such life cycle models to fully satisfy stakeholder needs. More complex life cycle models which address this are described in Life Cycle Models.
A Generic System Life Cycle Model
There is no single “one-size-fits-all” system life cycle model that can provide specific guidance for all project situations. Figure 1, adapted from (Lawson 2010, ISO/IEC 2008, and ISO/IEC 2010), provides a generic life cycle model that forms a starting point for the most common versions of pre-specified, evolutionary, sequential, opportunistic, and concurrent life cycle processes. The model is defined as a set of stages, within which technical and management activities are performed. The stages are terminated by decision gates where the key stakeholders decide whether to proceed into the next stage, to remain in the current stage, or to terminate or re-scope related projects.
Elaborated definitions of these stages are provided below, in the glossary, and in various other ways in subsequent articles.
The Concept Definition stage begins with a decision by a protagonist (individual or organization) to invest resources in a new or improved system. Inception begins with a set of stakeholders agreeing to the need for a system and exploring whether a new or modified system can be developed, in which the life cycle benefits are worth the investments in the life cycle costs. Activities include: developing the concept of operations and business case; determining the key stakeholders and their desired capabilities; negotiating the stakeholder requirements among the key stakeholders and selecting the system’s non-developmental items (NDIs).
The System Definition stage begins when the key stakeholders decide that the business needs and stakeholder requirements are sufficiently well defined to justify committing the resources necessary to define a whole system solution in sufficient detail to answer the life cycle cost questions identified in concept definition and provide a basis of system realization if appropriate. Activities include developing the system’s architecture; defining and agreeing levels of system requirements; developing systems-level life cycle plans and performing system analysis in order to illustrate the compatibility and feasibility of the resulting system definition. The transition into the system realization stage can lead to either single-pass or multiple-pass development.
It should be noted that the concept and system definition activities above describe activities performed by systems engineers when performing systems engineering. There is a very strong concurrency between proposing a problem situation or opportunity and describing one or more possible system solutions, as discussed in Systems Approach Applied to Engineered Systems. Other related definition activities include: prototyping or actual development of high-risk items to show evidence of system feasibility; collaboration with business analysts or performing mission effectiveness analyses to provide a viable business case for proceeding into realization; and modifications to realized systems to improve their production, support or utilization. These activities will generally happen through the system life cycle to handle system evolution, especially under multiple-pass development. This is discussed in more detail in the Life Cycle Models knowledge area.
The System Realization stage begins when the key stakeholders decide that the system elements and feasibility evidence are sufficiently low-risk to justify committing the resources necessary to develop and sustain the initial operational capability (IOC) or the single-pass development of the full operational capability (FOC). Activities include: construction of the developmental elements; integration of these with each other and with the non-developmental item (NDI) elements; verification and validation (V&V) of the elements and their integration as it proceeds; and preparing for the concurrent production, support, and utilization activities.
The System Production, Support, and Utilization (PSU) stages begins when the key stakeholders decide that the system life-cycle feasibility and safety illustrate a sufficiently low-risk level that justifies committing the resources necessary to produce, field, support, and utilize the system over its expected lifetime. The lifetimes of production, support, and utilization are likely to be different. Aftermarket support will generally continue after production is complete and users will often continue to use unsupported systems.
System Production involves the fabrication of system copies or versions and of associated aftermarket spare parts. It also includes production quality monitoring and improvement; product or service acceptance activities; and continuous production process improvement. It may include low-rate initial production (LRIP) to mature the production process or to promote the continued preservation of the production capability for future spikes in demand.
Systems Support includes various classes of maintenance: corrective (for defects), adaptive (for interoperability with independently evolving co-dependent systems), and perfective (for enhancement of performance, usability, or other key performance parameters). It also includes hot lines and responders for user or emergency support and the provisioning of needed consumables (gas, water, power, etc.). Its boundaries include some gray areas, such as the boundary between small system enhancements and the development of larger complementary new additions, and the boundary between rework/maintenance of earlier fielded increments in incremental or evolutionary development. Systems Support usually continues after System Production is terminated.
System Utilization includes the use of the system by operators, administrators, the general public, or systems above it in the system-of-interest hierarchy. It usually continues after Systems Support is terminated.
The System Retirement stage is often executed incrementally as system versions or elements become obsolete or are no longer economical to support and therefore undergo disposal or recycling of their content. Increasingly affordable considerations make system re-purposing an attractive alternative.
Applying the Life Cycle Model
Figure 1 shows just the single-step approach for proceeding through the stages of a system’s life cycle. In Life Cycle Models knowledge area we discuss examples of real world enterprises and their drivers, both technical and organizational. These have lead to a number of documented approaches for sequencing the life cycle stages to deal with some of the issues raised. The Life Cycle Models KA summarizes a number of incremental and evolutionary life cycle models, including their main strengths and weaknesses and also discusses criteria for choosing the best-fit approach.
In figure 1 we have listed key aechnical and management ctivities critical to successful completion of each stage. This is a useful way to illustrate the goals of each stage and gives an indication of how processes align with these stages. This can be important when considering how to plan for resources, milestones, etc. However, it is important to observe that the execution of process activities are not compartmentalized to particular life cycle stages (Lawson 2010). In Applying Life Cycle Processes we discuss a number of views on the nature of the inter-relationships between process activities within a life cycle model. In general, the technical and management activities are applied in accordance with the principles of concurrent , iteration and recursion described in the generic life cycle paradigm.
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.
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.
Lawson, H. 2010. A Journey Through the Systems Landscape. London, UK: College Publications.
Primary References
Forsberg, K., H. Mooz, H. Cotterman. 2005. Visualizing Project Management, 3rd Ed. Hoboken, NJ: J. Wiley & Sons.
INCOSE. 2012. Systems Engineering Handbook, 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.
Additional References
none.
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