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{{software development process|Core activities}}

In [[software engineering]], aA '''software development process''' or '''software development life cycle''' ('''SDLC''') isprescribes a process of planning and managingfor [[software development|developing]] [[software]]. It typically involvesdivides dividingan software developmentoverall workeffort into smaller, parallel, or sequential steps or sub-processes tothat improveare [[Softwareintended design|design]]to and/orensure [[Softwarehigh-quality product management|product management]]results. The methodologyprocess may include the pre-definition ofdescribe specific [[deliverable]]s and{{endash}} artifacts thatto arebe created and completed by a project team to develop or maintain an application.<ref name="CMS08">{{cite web |website=Centers for Medicare & Medicaid Services (CMS) Office of Information Service |url=http://www.cms.gov/Research-Statistics-Data-and-Systems/CMS-Information-Technology/XLC/Downloads/SelectingDevelopmentApproach.pdf |title=Selecting a development approach |publisher=United States Department of Health and Human Services (HHS) |orig-date=Original Issuance: February 17, 2005 |date=March 27, 2008 |access-date=October 27, 2008 |archive-url=https://web.archive.org/web/20120620212919/http://www.cms.gov/Research-Statistics-Data-and-Systems/CMS-Information-Technology/XLC/Downloads/SelectingDevelopmentApproach.pdf |archive-date=June 20, 2012 |url-status=dead}}</ref>

Although not strictly limited to it, software development process often refers to the high-level process that governs the development of a software system from its beginning to its end of life {{endash}} known as a methodology, model or framework. The [[system development life cycle]] (SDLC) describes the typical phases that a development effort goes through from the beginning to the end of life for a system {{endash}} including a software system. A methodology prescribes how [[engineer]]s go about their work in order to move the system through its life cycle. A methodology is a classification of processes or a blueprint for a process that is devised for the SDLC. For example, many processes can be classified as a spiral model.

Most modern development processes can be vaguely described as [[Agile software development|agile]]. Other methodologies include [[waterfall model|waterfall]], [[software prototyping|prototyping]], [[iterative and incremental development]], [[spiral development]], [[rapid application development]], and [[extreme programming]].

Software process and [[software quality]] are closely interrelated; some unexpected facets and effects have been observed in practice.<ref name="ieeesw">{{Cite journal | doi = 10.1109/MS.2015.87 | title = Software Process versus Design Quality: Tug of War? | journal = IEEE Software | volume = 32 | issue = 4 | pages = 7–11 | year = 2015 | last1 = Suryanarayana | first1 = Girish | doi-access = free }}</ref>

A life-cycle "model" is sometimes considered a more general term for a category of methodologies and a software development "process" is a particular instance as adopted by a specific organization.{{Citation needed|date=September 2020}} For example, many specific software development processes fit the spiral life-cycle model. The field is often considered a subset of the [[systems development life cycle]].

== History Methodology==

The SDLC drives the definition of a methodology in that a methodology must address the phases of the SDLC. Generally, a methodology is designed to result in a high-quality system that meets or exceeds expectations (requirements) and is delivered on time and within budget even though computer systems can be complex and integrate disparate components.<ref>{{cite web|url=http://foldoc.org/Systems+Development+Life+Cycle |title=Systems Development Life Cycle from |publisher=FOLDOC |access-date=2013-06-14}}</ref> Various methodologies have been devised, including [[Waterfall model|waterfall]], [[Spiral model|spiral]], [[Agile software development|agile]], [[Software prototyping#Throwaway prototyping|rapid prototyping]], [[Incremental development|incremental]], and synchronize and stabilize.<ref>{{cite web |date=May 2012 |title=Software Development Life Cycle (SDLC) |url=http://softwarelifecyclepros.com/wp-content/uploads/2012/05/Tutorial-Software-Development-LifeCycle-SDLC.pdf |access-date=2025-06-26 |website=softwarelifecyclepros.com }}</ref>

A major difference between methodologies is the degree to which the phases are sequential vs. iterative. Agile methodologies, such as [[Extreme Programming|XP]] and [[Scrum (development)|scrum]], focus on lightweight processes that allow for rapid changes.<ref>{{Cite web | url=https://aristeksystems.com/blog/sdlc-overview/| title=SDLC Overview: Models & Methodologies| access-date=2021-12-12}}</ref> [[Iterative and incremental development|Iterative]] methodologies, such as [[Rational Unified Process]] and [[dynamic systems development method]], focus on stabilizing project scope and iteratively expanding or improving products. Sequential or big-design-up-front (BDUF) models, such as waterfall, focus on complete and correct planning to guide larger projects and limit risks to successful and predictable results.<ref>{{Cite book |last=Arden |first=Trevor |title=Information technology applications |date=1991 |publisher=Pitman |isbn=978-0-273-03470-4 |___location=London}}</ref> [[Anamorphic development]] is guided by project scope and adaptive iterations. In scrum,<ref>{{cite web |url=https://www.scrum.org/resources/what-is-scrum |title=What is Scrum? |date=December 24, 2019 }}</ref> for example, one could say a single user story goes through all the phases of the SDLC within a two-week sprint. By contrast the waterfall methodology, where every business requirement{{Citation needed|date=August 2021}} is translated into feature/functional descriptions which are then all implemented typically over a period of months or longer.{{Citation needed|date=August 2021}}

The software development methodology framework did not emerge until the 1960s. According to Elliott (2004), the [[systems development life cycle]] can be considered to be the oldest formalized methodology framework for building [[information system]]s. The main idea of the software development life cycle has been "to pursue the development of information systems in a very deliberate, structured and methodical way, requiring each stage of the life cycle––from the inception of the idea to delivery of the final system––to be carried out rigidly and sequentially"<ref name="Ell04">{{cite book |author=Geoffrey Elliott |date=2004 |title=Global Business Information Technology: an integrated systems approach |publisher=Pearson Education |page=87}}</ref> within the context of the framework being applied. The main target of this methodology framework in the 1960s was "to develop large scale functional [[business system]]s in an age of large scale business conglomerates. Information systems activities revolved around heavy [[data processing]] and [[number crunching]] routines."<ref name=Ell04/>

A project can include both a [[project life cycle]] (PLC) and an SDLC, which describe different activities. According to Taylor (2004), "the project life cycle encompasses all the activities of the [[project]], while the systems development life cycle focuses on realizing the product [[requirement]]s".<ref>{{cite book |first=James |last=Taylor |year=2004 |title=Managing Information Technology Projects |page=39}}</ref>

'''Requirements gathering and analysis:'''

The first phase of the custom software development process involves understanding the client's requirements and objectives. This stage typically involves engaging in thorough discussions and conducting interviews with stakeholders to identify the desired features, functionalities, and overall scope of the software. The development team works closely with the client to analyze existing systems and workflows, determine technical feasibility, and define project milestones.

===History===

'''Planning and design:'''

The term ''SDLC'' is often used as an abbreviated version of ''SDLC methodology''. Further, some use ''SDLC'' and ''traditional SDLC'' to mean the waterfall methodology.

Once the requirements are understood, the custom software development team proceeds to create a comprehensive project plan. This plan outlines the development roadmap, including timelines, resource allocation, and deliverables. The software architecture and design are also established during this phase. User interface (UI) and user experience (UX) design elements are considered to ensure the software's usability, intuitiveness, and visual appeal.

According to Elliott (2004), SDLC "originated in the 1960s, to develop large scale functional [[business systems]] in an age of large scale [[business conglomerate]]s. Information systems activities revolved around heavy [[data processing]] and [[number crunching]] routines".<ref name="Ell04"/> The [[structured systems analysis and design method]] (SSADM) was produced for the UK government [[Office of Government Commerce]] in the 1980s. Ever since, according to Elliott (2004), "the traditional life cycle approaches to systems development have been increasingly replaced with alternative approaches and frameworks, which attempted to overcome some of the inherent deficiencies of the traditional SDLC".<ref name="Ell04"/> The main idea of the SDLC has been "to pursue the development of information systems in a very deliberate, structured and methodical way, requiring each stage of the life cycle––from the inception of the idea to delivery of the final system––to be carried out rigidly and sequentially"<ref name="Ell04">{{cite book |author=Geoffrey Elliott |date=2004 |title=Global Business Information Technology: an integrated systems approach |publisher=Pearson Education |page=87}}</ref> within the context of the framework being applied.

'''Development:'''

With the planning and design in place, the development team begins the coding process. This phase involves [[writing]], testing, and debugging the software code. Agile methodologies, such as scrum or kanban, are often employed to promote flexibility, collaboration, and iterative development. Regular communication between the development team and the client ensures transparency and enables quick feedback and adjustments.

Other methodologies were devised later:

'''Testing and quality assurance:'''

To ensure the software's reliability, performance, and security, rigorous testing and quality assurance (QA) processes are carried out. Different testing techniques, including unit testing, integration testing, system testing, and user acceptance testing, are employed to identify and rectify any issues or bugs. QA activities aim to validate the software against the predefined requirements, ensuring that it functions as intended.

'''Deployment and implementation:'''

Once the software passes the testing phase, it is ready for deployment and implementation. The development team assists the client in setting up the software environment, migrating data if necessary, and configuring the system. User training and documentation are also provided to ensure a smooth transition and enable users to maximize the software's potential.

'''Maintenance and support:'''

After the software is deployed, ongoing maintenance and support become crucial to address any issues, enhance performance, and incorporate future enhancements. Regular updates, bug fixes, and security patches are released to keep the software up-to-date and secure. This phase also involves providing technical support to end users and addressing their queries or concerns.

Methodologies, processes, and frameworks range from specific prescriptive steps that can be used directly by an organization in day-to-day work, to flexible frameworks that an organization uses to generate a custom set of steps tailored to the needs of a specific project or group. In some cases, a "sponsor" or "maintenance" organization distributes an official set of documents that describe the process. Specific examples include:

; 1970s

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* [[DevOps]]

Since DSDM in 1994, all of the methodologies on the above list except RUP have been agile methodologies - yet many organizations, especially governments, still use pre-agile processes (often waterfall or similar). Software process and [[software quality]] are closely interrelated; some unexpected facets and effects have been observed in practice.<ref name="ieeesw">{{Cite journal | doi = 10.1109/MS.2015.87 | title = Software Process versus Design Quality: Tug of War? | journal = IEEE Software | volume = 32 | issue = 4 | pages = 7–11 | year = 2015 | last1 = Suryanarayana | first1 = Girish | doi-access = free }}</ref>

===Examples===

Among these, another software development process has been established in [[Open-source software|open source]]. The adoption of these best practices known and established processes within the confines of a company is called [[inner source]].

The following are notable methodologies somewhat ordered by popularity.

== Prototyping ==

; Agile

[[Software prototyping]] is about creating prototypes, i.e. incomplete versions of the software program being developed.

[[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.

; Waterfall

The basic principles are:<ref name=CMS08/>

The [[waterfall model]] is a sequential development approach, in which development flows one-way (like a waterfall) through the SDLC phases.

; Spiral

* 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)).

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.

* 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.

; Incremental

A basic understanding of the fundamental business problem is necessary to avoid solving the wrong problems, but this is true for all software methodologies.

[[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

== Methodologies ==

[[Software prototyping]] is about creating prototypes, i.e. incomplete versions of the software program being developed.

; Rapid

=== Agile development ===

[[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.

{{main|Agile software development}}

; Shape Up

"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.

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>

; Chaos

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.

[[Chaos model]] has one main rule: always resolve the most important issue first.

; Incremental funding

The Agile model also includes the following software development processes:

[[Incremental funding methodology]] - an iterative approach.

; Lightweight

* [[Dynamic systems development method]] (DSDM)

[[Lightweight methodology]] - a general term for methods that only have a few rules and practices.

* [[Kanban (development)|Kanban]]

* [[Scrum (development)|Scrum]]

* [[Lean software development]]

; Structured systems analysis and design

=== Continuous integration ===

[[Structured systems analysis and design method]] - a specific version of waterfall.

{{main|Continuous integration}}

; Slow programming

[[Continuous integration]] is the practice of merging all developer working copies to a shared [[Trunk (software)|mainline]] several times a day.<ref name=CI0>{{cite book

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.

|title=Continuous Integration: Improving Software Quality and Reducing Risk

|author1=Paul M. Duvall

|author2=Steve Matyas

|author3=[[Andrew Glover]]

|isbn=978-0-321-33638-5

|publisher=[[Addison-Wesley Professional]]

|date=2007

}}

</ref>

[[Grady Booch]] first named and proposed CI in [[Booch method|his 1991 method]],<ref>{{cite book |last= Booch |first= Grady |author-link= Grady Booch |year= 1991 |title=Object Oriented Design: With Applications |url= https://books.google.com/books?id=w5VQAAAAMAAJ&q=continuous+integration+inauthor:grady+inauthor:booch |publisher= [[Benjamin Cummings]] |page= 209 |isbn= 9780805300918 |access-date= August 18, 2014 }}</ref> although he did not advocate integrating several times a day. [[Extreme programming]] (XP) adopted the concept of CI and did advocate integrating more than once per day – perhaps as many as tens of times per day.

; V-Model

=== Incremental development ===

[[V-Model (software development)]] - an extension of the waterfall model.

{{main|Iterative and incremental development}}

; Unified Process

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.

[[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.

===Comparison===

There are three main variants of incremental development:<ref name=CMS08/>

{{More citations needed section|date=January 2024}}

The waterfall model describes the SDLC phases such that each builds on the result of the previous one.<ref name="US DJ03">US Department of Justice (2003). [https://www.justice.gov/archive/jmd/irm/lifecycle/table.htm INFORMATION RESOURCES MANAGEMENT] Chapter 1. Introduction.</ref><ref name="EverettSoftware07">{{cite book |chapter-url=https://books.google.com/books?id=z8UdPmvkBHEC&pg=PA29 |chapter=Chapter 2: The Software Development Life Cycle |title=Software Testing: Testing Across the Entire Software Development Life Cycle |author=Everatt, G.D. |author2=McLeod, R Jr |publisher=John Wiley & Sons |pages=29–58 |year=2007 |isbn=9780470146347}}</ref><ref name="UnhelkarTheArt16">{{cite book |url=https://books.google.com/books?id=ZqnMBQAAQBAJ&pg=PA56 |title=The Art of Agile Practice: A Composite Approach for Projects and Organizations |author=Unhelkar, B. |publisher=CRC Press |pages=56–59 |year=2016 |isbn=9781439851197}}</ref><ref name="LandPract12">{{cite book |url=https://books.google.com/books?id=SsBF_lVbK_gC&pg=PA341 |title=Practical Support for Lean Six Sigma Software Process Definition: Using IEEE Software Engineering Standards |author=Land, S.K.|author-link= Susan K. Land |author2=Smith, D.B. |author3=Walz, J.W. |publisher=John Wiley & Sons |pages=341–3 |year=2012 |isbn=9780470289952}}</ref> Not every project requires that the phases be sequential. For relatively simple projects, phases may be combined or overlapping.<ref name="US DJ03" /> Alternative methodologies to waterfall are described and compared below.<ref name="Post, G. 2006">Post, G., & Anderson, D., (2006). ''Management information systems: Solving business problems with information technology''. (4th ed.). New York: McGraw-Hill Irwin.</ref>

# 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.

{| class="wikitable" style="margin:auto;"

=== Rapid application development ===

|+ Comparison of methodologies

{{main|Rapid application development}}

|-

! style="width:5%;"|

!| Waterfall

!| [[Rapid application development| RAD]]

!| [[Open-source software development| Open source]]

!| [[Object-oriented programming|OOP]]

!| [[Joint applications development| JAD]]

!| [[Software prototyping| proto-typing]]

!| [[End-user development| End User]]

|-

| Control

| Formal

| MIS

| Weak

| Standards

| Joint

| User

| User

|-

| Time frame

| Long

| Short

| Medium

| Any

| Medium

| Short

| Short

–

|-

| Users

| Many

| Few

| Few

| Varies

| Few

| One or two

| One

|-

| MIS staff

| Many

| Few

| Hundreds

| Split

| Few

| One or two

| None

|-

| Transaction/[[Decision support system|DSS]]

| Transaction

| Both

| Both

| Both

| DSS

| DSS

| DSS

|-

| Interface

| Minimal

| Minimal

| Weak

| Windows

| Crucial

| Crucial

| Crucial

|-

| Documentation and training

| Vital

| Limited

| Internal

| In Objects

| Limited

| Weak

| None

|-

| Integrity and security

| Vital

| Vital

| Unknown

| In Objects

| Limited

| Weak

| Weak

|-

| Reusability

| Limited

| Some

| Maybe

| Vital

| Limited

| Weak

| None

|}

== Process meta-models ==

[[File:RADModel.JPG|thumb|Rapid Application Development (RAD) Model]]

{{Further|Process patterns}}

Some [[process model]]s are abstract descriptions for evaluating, comparing, and improving the specific process adopted by an organization.

[[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.

; ISO/IEC 12207

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/>

[[ISO/IEC 12207]] is the international standard describing the method to select, implement, and monitor the life cycle for software.

; Capability Maturity Model Integration

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 [[Capability Maturity Model Integration]] (CMMI) is one of the leading models and is based on best practices. Independent assessments grade organizations on how well they follow their defined processes, not on the quality of those processes or the software produced. CMMI has replaced [[Capability Maturity Model|CMM]].

; ISO 9000

The basic principles of rapid application development are:<ref name=CMS08/>

[[ISO 9000]] describes standards for a formally organized process to manufacture a product and the methods of managing and monitoring progress. Although the standard was originally created for the manufacturing sector, ISO 9000 standards have been applied to software development as well. Like CMMI, certification with ISO 9000 does not guarantee the quality of the end result, only that formalized business processes have been followed.

; ISO/IEC 15504

* Key objective is for fast development and delivery of a high-quality system at a relatively low investment cost.

[[ISO/IEC 15504]] ''Information technology—Process assessment'', a.k.a. Software Process Improvement Capability Determination (SPICE), is a framework for the assessment of software processes. This standard is aimed at setting out a clear model for process comparison. SPICE is used much like CMMI. It models processes to manage, control, guide, and monitor software development. This model is then used to measure what a development organization or project team actually does during software development. This information is analyzed to identify weaknesses and drive improvement. It also identifies strengths that can be continued or integrated into common practice for that organization or team.

* 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.

; ISO/IEC 24744

=== Waterfall development ===

[[ISO/IEC 24744]] ''Software Engineering—Metamodel for Development Methodologies'', is a power type-based metamodel for software development methodologies.

{{main|Waterfall model}}

; Soft systems methodology

[[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.]]

[[Soft systems methodology]] is a general method for improving management processes.

; Method engineering

The waterfall model is a sequential development approach, in which development is seen as flowing steadily downwards (like a waterfall) through several phases, typically:

[[Method engineering]] is a general method for improving information system processes.

* [[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 }}</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>

=== 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>

=== Advanced methodologies ===

Other high-level software project methodologies include:

* [[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>

* [[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 ==

Some "[[process model]]s" are abstract descriptions for evaluating, comparing, and improving the specific process adopted by an organization.

* [[ISO/IEC 12207]] is the international standard describing the method to select, implement, and monitor the life cycle for software.

* The [[Capability Maturity Model Integration]] (CMMI) is one of the leading models and is based on best practices. Independent assessments grade organizations on how well they follow their defined processes, not on the quality of those processes or the software produced. CMMI has replaced [[Capability Maturity Model|CMM]].

* [[ISO 9000]] describes standards for a formally organized process to manufacture a product and the methods of managing and monitoring progress. Although the standard was originally created for the manufacturing sector, ISO 9000 standards have been applied to software development as well. Like CMMI, certification with ISO 9000 does not guarantee the quality of the end result, only that formalized business processes have been followed.

* [[ISO/IEC 15504]] ''Information technology—Process assessment is'' also known as Software Process Improvement Capability Determination (SPICE), is a "framework for the assessment of software processes". This standard is aimed at setting out a clear model for process comparison. SPICE is used much like CMMI. It models processes to manage, control, guide, and monitor software development. This model is then used to measure what a development organization or project team actually does during software development. This information is analyzed to identify weaknesses and drive improvement. It also identifies strengths that can be continued or integrated into common practice for that organization or team.

* [[ISO/IEC 24744]] ''Software Engineering—Metamodel for Development Methodologies'', is a power type-based metamodel for software development methodologies.

* [[Soft systems methodology]] - a general method for improving management processes.

* [[Method engineering]] - a general method for improving information system processes.

{{Further|Process patterns}}

== See also ==

<!-- Please don't list individual software development methodologies here. Instead, integrate them in the text above or in the current articles mentioned -->

* [[Computer-aided software engineering]]

* [[Systems development life cycle]]

* [[Computer-aided software engineering]] (some of these tools support specific methodologies)

* [[List of software development philosophies]]

* [[Outline of software engineering]]

* [[Software project management|Software Project Management]]

* [[Software development]]

* [[Software development effort estimation]]

* [[Software documentation]]

* [[Software project management]]

* [[Software release life cycle]]

* [[Top-down and bottom-up design#Computer science]]

== References ==