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The following are notable methodologies somewhat ordered by popularity.
===; Agile development ===
[[Agile software development]] refers to a group of frameworks based on iterative development, where requirements and solutions evolve via collaboration between self-organizing cross-functional teams. The term was coined in the year 2001 when the [[Agile Manifesto]] was formulated.
{{main|Agile software development}}
; Waterfall
"Agile software development" refers to a group of software development frameworks based on iterative development, where requirements and solutions evolve via collaboration between self-organizing cross-functional teams. The term was coined in the year 2001 when the [[Agile Manifesto]] was formulated.
The [[waterfall model]] is a sequential development approach, in which development flows one-way (like a waterfall) through the SDLC phases.
; Spiral
Agile software development uses iterative development as a basis but advocates a lighter and more people-centric viewpoint than traditional approaches. Agile processes fundamentally incorporate iteration and the continuous feedback that it provides to successively refine and deliver a software system.
In 1988, [[Barry Boehm]] published a software system development [[spiral model]], which combines key aspects of the waterfall model and [[rapid application development| rapid prototyping]], in an effort to combine advantages of [[top-down and bottom-up design| top-down and bottom-up]] concepts. It emphases a key area many felt had been neglected by other methodologies: deliberate iterative risk analysis, particularly suited to large-scale complex systems.
; Incremental
The Agile model also includes the following software development processes:
[[Iterative and incremental development|Various methods combine linear and iterative methodologies]], with the primary objective of reducing inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process.
; Prototyping
* [[Dynamic systems development method]] (DSDM)
* [[Kanban (development)|Kanban]]
* [[Scrum (development)|Scrum]]
* [[Lean software development]]
=== Waterfall development ===
{{main|Waterfall model}}
[[File:Waterfall model.svg|thumb|The activities of the software development process represented in the [[waterfall model]]. There are several other models to represent this process.]]
The waterfall model is a sequential development approach, in which development is seen as flowing steadily downwards (like a waterfall) through several phases, typically:
* [[Requirements analysis]] resulting in a [[software requirements specification]]
* [[Software design]]
* [[Computer programming|Implementation]]
* [[Software testing|Testing]]
* [[System integration|Integration]], if there are multiple subsystems
* [[Software deployment|Deployment]] (or [[Installation (computer programs)|Installation]])
* [[Software maintenance|Maintenance]]
The first formal description of the method is often cited as an article published by [[Winston W. Royce]]<ref>{{cite web |url=http://cartoon.iguw.tuwien.ac.at/fit/fit01/wasserfall/entstehung.html |title=Wasserfallmodell > Entstehungskontext |author=Markus Rerych |website=Institut für Gestaltungs- und Wirkungsforschung, TU-Wien |language=German |access-date=November 28, 2007}}</ref> in 1970, although Royce did not use the term "waterfall" in this article. Royce presented this model as an example of a flawed, non-working model.<ref>{{cite web |author=Conrad Weisert |url=http://www.idinews.com/waterfall.html |title=Waterfall methodology: there's no such thing! |archive-url=https://web.archive.org/web/20220802131155/http://www.idinews.com/waterfall.html |archive-date=August 2, 2022 |url-status=dead}}</ref>
The basic principles are:<ref name=CMS08/>
* The Project is divided into sequential phases, with some overlap and splashback acceptable between phases.
* Emphasis is on planning, time schedules, target dates, budgets, and implementation of an entire system at one time.
* Tight control is maintained over the life of the project via extensive written documentation, formal reviews, and approval/signoff by the user and [[information technology management]] occurring at the end of most phases before beginning the next phase. Written documentation is an explicit deliverable of each phase.
The waterfall model is a traditional engineering approach applied to software engineering. A strict waterfall approach discourages revisiting and revising any prior phase once it is complete. {{says who?|date=January 2021}} This "inflexibility" in a pure waterfall model has been a source of criticism by supporters of other more "flexible" models. It has been widely blamed for several large-scale government projects running over budget, over time and sometimes failing to deliver on requirements due to the [[big design up front]] approach.{{says who?|date=January 2021}} Except when contractually required, the waterfall model has been largely superseded by more flexible and versatile methodologies developed specifically for software development.{{says who?|date=January 2021}} See [[Waterfall model#Criticism|Criticism of waterfall model]].
=== Spiral development ===
[[File:Spiral model (Boehm, 1988).svg|thumb|400px|Spiral model (Boehm, 1988)]]
{{main|Spiral model}}
In 1988, [[Barry Boehm]] published a formal software system development "spiral model," which combines some key aspects of the [[waterfall model]] and [[rapid application development|rapid prototyping]] methodologies, in an effort to combine advantages of [[top-down and bottom-up design|top-down and bottom-up]] concepts. It provided emphasis on a key area many felt had been neglected by other methodologies: deliberate iterative risk analysis, particularly suited to large-scale complex systems.
The basic principles are:<ref name=CMS08/>
* Focus is on risk assessment and on minimizing project risk by breaking a project into smaller segments and providing more ease-of-change during the development process, as well as providing the opportunity to evaluate risks and weigh consideration of project continuation throughout the life cycle.
* "Each cycle involves a progression through the same sequence of steps, for each part of the product and for each of its levels of elaboration, from an overall concept-of-operation document down to the coding of each individual program."<ref name="BB86">{{cite journal |author=Barry Boehm |author-link=Barry Boehm |url=http://doi.acm.org/10.1145/12944.12948 |title=A Spiral Model of Software Development and Enhancement |journal=ACM SIGSOFT Software Engineering Notes |publisher=[[Association for Computing Machinery]] |volume=11 |issue=4 |pages=14–24 |date=August 1986|doi=10.1145/12944.12948 |s2cid=1781829 |url-access=subscription }}</ref>
* Each trip around the spiral traverses four basic quadrants: (1) determine objectives, alternatives, and constraints of the iteration, and (2) evaluate alternatives; Identify and resolve risks; (3) develop and verify deliverables from the iteration; and (4) plan the next iteration.<ref name="RT-BB86">{{cite book |author1=Richard H. Thayer |author2=Barry W. Boehm |author2-link=Barry Boehm |date=1986 |title=Tutorial: software engineering project management |publisher=Computer Society Press of the IEEE |page=130}}</ref>
* Begin each cycle with an identification of stakeholders and their "win conditions", and end each cycle with review and commitment.<ref>{{cite book |author=Barry W. Boehm |author-link=Barry Boehm |date=2000 |title=Software cost estimation with Cocomo II: Volume 1}}</ref>
=== Incremental development ===
{{main|Iterative and incremental development}}
Various methods are acceptable for combining linear and iterative systems development methodologies, with the primary objective of each being to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process.
There are three main variants of incremental development:<ref name=CMS08/>
# A series of mini-waterfalls are performed, where all phases of the waterfall are completed for a small part of a system, before proceeding to the next increment, or
# Overall requirements are defined before proceeding to evolutionary, mini-waterfall development of individual increments of a system, or
# The initial software concept, requirements analysis, and design of architecture and system core are defined via waterfall, followed by incremental implementation, which culminates in installing the final version, a working system.
=== Prototyping ===
[[Software prototyping]] is about creating prototypes, i.e. incomplete versions of the software program being developed.
; Rapid
The basic principles are:<ref name=CMS08/>
[[Rapid application development]] (RAD) is a methodology which favors [[iterative development]] and the rapid construction of [[prototype]]s instead of large amounts of up-front planning. The "planning" of software developed using RAD is interleaved with writing the software itself. The lack of extensive pre-planning generally allows software to be written much faster and makes it easier to change requirements.
; Shape Up
* Prototyping is not a standalone, complete development methodology, but rather an approach to try out particular features in the context of a full methodology (such as incremental, spiral, or rapid application development (RAD)).
Shape Up is a software development approach introduced by [[Basecamp (company)|Basecamp]] in 2018. It is a set of principles and techniques that Basecamp developed internally to overcome the problem of projects dragging on with no clear end. Its primary target audience is remote teams. Shape Up has no estimation and velocity tracking, backlogs, or sprints, unlike [[Waterfall model|waterfall]], [[Agile software development|agile]], or [[Scrum (software development)|scrum]]. Instead, those concepts are replaced with appetite, betting, and cycles. As of 2022, besides Basecamp, notable organizations that have adopted Shape Up include UserVoice and Block.<ref>{{Cite web |title=Foreword by Jason Fried {{!}} Shape Up |url=https://basecamp.com/shapeup/0.1-foreword |access-date=September 11, 2022 |website=basecamp.com}}</ref><ref>{{Cite web |title=Is Shape Up just a nice theory? |url=https://www.curiouslab.io/blog/is-shape-up-just-a-nice-theory |access-date=September 12, 2022 |website=Curious Lab |language=en-AU}}</ref>
* Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease of change during the development process.
* The client is involved throughout the development process, which increases the likelihood of client acceptance of the final implementation.
* While some prototypes are developed with the expectation that they will be discarded, it is possible in some cases to evolve from prototype to working system.
; Chaos
A basic understanding of the fundamental business problem is necessary to avoid solving the wrong problems, but this is true for all software methodologies.
[[Chaos model]] has one main rule: always resolve the most important issue first.
; Incremental funding
=== Rapid application development ===
[[Incremental funding methodology]] - an iterative approach.
{{main|Rapid application development}}
; Lightweight
[[File:RADModel.JPG|thumb|Rapid Application Development (RAD) Model]]
[[Lightweight methodology]] - a general term for methods that only have a few rules and practices.
; Structured systems analysis and design
[[Rapid application development]] (RAD) is a software development methodology, which favors [[iterative development]] and the rapid construction of [[prototype]]s instead of large amounts of up-front planning. The "planning" of software developed using RAD is interleaved with writing the software itself. The lack of extensive pre-planning generally allows software to be written much faster and makes it easier to change requirements.
[[Structured systems analysis and design method]] - a specific version of waterfall.
The rapid development process starts with the development of preliminary [[data model]]s and [[business process model]]s using [[structured technique]]s. In the next stage, requirements are verified using prototyping, eventually to refine the data and process models. These stages are repeated iteratively; further development results in "a combined business requirements and technical design statement to be used for constructing new systems".<ref name=WBD04/>
The term was first used to describe a software development process introduced by [[James Martin (author)|James Martin]] in 1991. According to Whitten (2003), it is a merger of various [[Structured Analysis and Design Technique|structured techniques]], especially data-driven [[information technology engineering]], with prototyping techniques to accelerate software systems development.<ref name="WBD04">[[Whitten, Jeffrey L.]]; [[Lonnie D. Bentley]], [[Kevin C. Dittman]]. (2003). ''Systems Analysis and Design Methods''. 6th edition. {{ISBN|0-256-19906-X}}.</ref>
The basic principles of rapid application development are:<ref name=CMS08/>
* Key objective is for fast development and delivery of a high-quality system at a relatively low investment cost.
* Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease of change during the development process.
* Aims to produce high-quality systems quickly, primarily via iterative Prototyping (at any stage of development), active user involvement, and computerized development tools. These tools may include [[graphical user interface]] (GUI) builders, [[Computer Aided Software Engineering]] (CASE) tools, [[Database Management System]]s (DBMS), [[fourth-generation programming language]]s, code generators, and object-oriented techniques.
* Key emphasis is on fulfilling the business need, while technological or engineering excellence is of lesser importance.
* Project control involves prioritizing development and defining delivery deadlines or “timeboxes”. If the project starts to slip, the emphasis is on reducing requirements to fit the timebox, not on increasing the deadline.
* Generally includes [[joint application design]] (JAD), where users are intensely involved in [[system design]], via consensus building in either structured workshops, or electronically facilitated interaction.
* Active user involvement is imperative.
* Iteratively produces production software, as opposed to a throwaway prototype.
* Produces documentation necessary to facilitate future development and maintenance.
* Standard systems analysis and design methods can be fitted into this framework.
=== Shape Up ===
Shape Up is a software development approach introduced by [[Basecamp (company)|Basecamp]] in 2018. It is a set of principles and techniques that Basecamp developed internally to overcome the problem of projects dragging on with no clear end. Its primary target audience is remote teams. Shape Up has no estimation and velocity tracking, backlogs, or sprints, unlike [[Waterfall model|waterfall]], [[Agile software development|agile]], or [[Scrum (software development)|scrum]]. Instead, those concepts are replaced with appetite, betting, and cycles. As of 2022, besides Basecamp, notable organizations that have adopted Shape Up include UserVoice and Block.<ref>{{Cite web |title=Foreword by Jason Fried {{!}} Shape Up |url=https://basecamp.com/shapeup/0.1-foreword |access-date=September 11, 2022 |website=basecamp.com}}</ref><ref>{{Cite web |title=Is Shape Up just a nice theory? |url=https://www.curiouslab.io/blog/is-shape-up-just-a-nice-theory |access-date=September 12, 2022 |website=Curious Lab |language=en-AU}}</ref>
; Slow programming
=== Advanced methodologies ===
As part of the larger [[Slow movement (culture)|slow movement]], emphasizes careful and gradual work without (or minimal) time pressures. Slow programming aims to avoid bugs and overly quick release schedules.
; V-Model
Other high-level software project methodologies include:
[[V-Model (software development)]] - an extension of the waterfall model.
; Unified Process
* [[Behavior-driven development]] and business process management.<ref name="ieeeswbdd">{{Cite journal | doi= 10.1109/MS.2016.117 | title = Modeling Test Cases in BPMN for Behavior-Driven Development | journal = IEEE Software | volume = 33 | issue = 5 | pages = 15–21 | year = 2016 |author1=Lübke, Daniel |author2=van Lessen, Tammo | s2cid = 14539297 }}</ref>
[[Unified Process]] (UP) is an iterative software development methodology framework, based on [[Unified Modeling Language]] (UML). UP organizes the development of software into four phases, each consisting of one or more executable iterations of the software at that stage of development: inception, elaboration, construction, and guidelines.
* [[Chaos model]] - The main rule always resolves the most important issue first.
* [[Incremental funding methodology]] - an iterative approach
* [[Lightweight methodology]] - a general term for methods that only have a few rules and practices
* [[Structured systems analysis and design method]] - a specific version of waterfall
* Slow programming, as part of the larger [[Slow movement (culture)|Slow Movement]], emphasizes careful and gradual work without (or minimal) time pressures. Slow programming aims to avoid bugs and overly quick release schedules.
* [[V-Model (software development)]] - an extension of the waterfall model
* [[Unified Process]] (UP) is an iterative software development methodology framework, based on [[Unified Modeling Language]] (UML). UP organizes the development of software into four phases, each consisting of one or more executable iterations of the software at that stage of development: inception, elaboration, construction, and guidelines.
== Process meta-models ==
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