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#REDIRECT [[Software development process]]
A '''software development methodology''' or ''system development methodology'' in [[software engineering]] is a framework that is used to structure, plan, and control the [[software development process|process of developing]] an [[information system]]<ref name= "CMS08">[http://www.cms.hhs.gov/SystemLifecycleFramework/Downloads/SelectingDevelopmentApproach.pdf SELECTING A DEVELOPMENT APPROACH]. Revalidated: March 27, 2008. Retrieved 27 Oct 2008.</ref>.
[[Image:Software development methodologies.jpg|thumb|480px|The three basic patterns in software development methodologies.]]
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== Overview ==
A software development methodology refers to the [[framework]] that is used to [[structure]], [[plan]], and [[control]] the [[process]] of developing an information system. A wide variety of such frameworks have evolved over the years, each with its own recognized strengths and weaknesses. One system development methodology is not necessarily suitable for use by all projects. Each of the available methodologies is best suited to specific kinds of projects, based on various technical, organizational, project and team considerations.<ref name= "CMS08"/>
The framework of a software development methodology consists of:
* A [[List of software development philosophies|software development philosophy]], with the approach or approaches of the software development process
* Multiple tools, models and methods, to assist in the software development process.
These frameworks are often bound to some kind of organization, which further develops, supports the use, and promotes the methodology. The methodology is often documented in some kind of formal documentation.
== History ==
One of the oldest software development tools is [[flowchart]]ing, which developed since the 1920s. The software development methodology has emerged since the 1960s. The oldest formalized [[methodology]] for building [[information system]]s is the [[Systems development life cycle]]. The main idea was to pursue the development of information systems in a very deliberate, structured and methodical way, reiterating each stage of the [[life cycle]]. The traditional Systems development life cycle originated in the 1960s to develop large scale functional [[business system]]s in an age of large scale business conglomerates. Information systems activities resolved around heavy [[data processing]] and [[number crunching]] routines.<ref name="Ell04"> Geoffrey Elliott (2004) ''Global Business Information Technology''. p.87.</ref>
=== Specific software development methodologies ===
;1970s
* [[Structured programming]] since 1969
;1980s
* [[Structured Systems Analysis and Design Methodology]] (SSADM) from 1980 onwards
;1990s
* [[Object-oriented programming]] (OOP) has been developed since the early 1960s, and developed as the dominant programming methodology during the mid-1990s.
* [[Rapid application development]] (RAD) since 1991.
* [[Scrum (development)|Scrum]] (development), since the late 1990s
* [[Team_Software_Process|Team software process]] developed by Watts Humphrey at the [[SEI]]
;2000s
* [[Extreme Programming]] since 1999
* [[Rational Unified Process]] (RUP) since 2003.
* [[Agile Unified Process]] (AUP) since 2005 by [[Scott Ambler]]
== Software development approaches ==
Every software development methodology has more or less its own approach to [[software development]]. There is a set of more general approaches, which are developed into several specific methodologies. These approaches are:<ref name= "CMS08"/>
* Waterfall: linear framework type
* Prototyping: iterative framework type
* Incremental : combination of linear and iterative framework type
* Spiral : combination linear and iterative framework type
* Rapid Application Development (RAD) : Iterative Framework Type
=== Waterfall model ===
The [[waterfall model]] is a sequential development process, in which development is seen as flowing steadily downwards (like a waterfall) through the phases of requirements analysis, design, implementation, testing (validation), integration, and maintenance. The first formal description of the waterfall model is often cited to be an article published by [[Winston W. Royce]]<ref>[http://cartoon.iguw.tuwien.ac.at/fit/fit01/wasserfall/entstehung.html Wasserfallmodell > Entstehungskontext], Markus Rerych, Institut für Gestaltungs- und Wirkungsforschung, TU-Wien. Accessed on line [[November 28]], [[2007]].</ref> in 1970 although Royce did not use the term "waterfall" in this article.
Basic principles of the waterfall model are:<ref name= "CMS08"/>
* 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 through the use of extensive written documentation, as well as through formal reviews and approval/signoff by the user and information technology management occurring at the end of most phases before beginning the next phase.
=== Prototyping ===
[[Software prototyping]], is the framework of activities during [[software development]] of creating prototypes, i.e., incomplete versions of the software program being developed.
Basic principles of prototyping are:<ref name= "CMS08"/>
* Not a standalone, complete development methodology, but rather an approach to handling selected portions of a larger, more traditional development methodology (i.e. Incremental, Spiral, or Rapid Application Development (RAD)).
* Attempts to reduce inherent project risk by breaking a project into smaller segments and providing more ease-of-change during the development process.
* User is involved throughout the process, which increases the likelihood of user acceptance of the final implementation.
* Small-scale mock-ups of the system are developed following an iterative modification process until the prototype evolves to meet the users’ requirements.
* While most prototypes are developed with the expectation that they will be discarded, it is possible in some cases to evolve from prototype to working system.
* A basic understanding of the fundamental business problem is necessary to avoid solving the wrong problem.
=== Incremental ===
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.
Basic principles of incremental development are:<ref name= "CMS08"/>
* A series of mini-Waterfalls are performed, where all phases of the Waterfall development model are completed for a small part of the systems, before proceeding to the next incremental, or
* Overall requirements are defined before proceeding to evolutionary, mini-Waterfall development of individual increments of the system, or
* The initial software concept, requirements analysis, and design of architecture and system core are defined using the Waterfall approach, followed by iterative Prototyping, which culminates in installation of the final prototype (i.e., working system).
=== Spiral ===
The [[spiral model]] is a [[software development process]] combining elements of both [[design]] and [[prototyping]]-in-stages, in an effort to combine advantages of [[Top-down and bottom-up design|top-down and bottom-up]] concepts.
Basic principles:<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 portion 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>(Boehm, 1986)</ref>
* Each trip around the spiral traverses four basic quadarants: (1) determine objectives, alternatives, and constrainst of the iteration; (2) Evaluate alternatives; Identify and resolve risks; (3) develop and verify deliverables from the iteration; and (4) plan the next iteration. <ref>(Boehm, 1986 and 1988)</ref>
* Begin each cycle with an identification of stakeholders and their win conditions, and end each cycle with review and commitment. <ref>(Boehm, 2000)</ref>
=== Rapid Application Development (RAD) ===
[[Rapid Application Development]] (RAD) is a software development methodology, which involves iterative development and the construction of [[prototype]]s. Rapid application development is a term originally used to describe a [[software development process]] introduced by [[James Martin (author)|James Martin]] in 1991.
Basic principles:<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 through the use of 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 languages, 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, emphasis is on reducing requirements to fit the timebox, not in increasing the deadline.
* Generally includes [[Joint Application Development]] (JAD), where users are intensely involved in [[system design]], either through consensus building in structured workshops, or through 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 techniques can be fitted into this framework.
=== Other software development approaches ===
<!-- This section should only list basic software development methodology (approaches) that are developed into multiple software development methodologies.-->
Other method concepts are:
* [[Object oriented]] development methodologies, such as Grady Booch's [[Object-oriented design]] (OOD), also known as object-oriented analysis and design (OOAD). The Booch model includes six diagrams: class, object, state transition, interaction, module, and process.<ref>Georges Gauthier Merx & Ronald J. Norman (2006). ''Unified Software Engineering with Java''. p.201.</ref>
* [[Top-down programming]]: evolved in the 1970s by IBM researcher [[Harlan Mills]] (and [[Niklaus Wirth]]) in developed [[structured programming]].
* [[Unified Process]] (UP) is an iterative software development methodology approach, 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. There are a number of tools and products available designed to facilitate UP implementation. One of the more popular versions of UP is the Rational Unified Process (RUP).
== Software development methodology topics ==
=== View model ===
[[File:TEAF Matrix of Views and Perspectives.jpg|thumb|360px|The [[TEAF]] Matrix of Views and Perspectives.]]
A [[View model]] is framework which provides the [[viewpoint]]s on the [[system]] and its [[environment]], to be used in the [[software development process]]. It is a graphical representation of the underlying semantics of a [[view]].
The purpose of [[viewpoint]]s and [[view]]s is to enable human engineers to comprehend very [[complex system]]s, and to organize the elements of the problem and the solution around domains of [[expertise]]. In the [[engineering]] of physically-intensive systems, viewpoints often correspond to capabilities and responsibilities within the engineering organization.<ref name="NIST2003"> Edward J. Barkmeyer ea (2003). [http://www.mel.nist.gov/msidlibrary/doc/AMIS-Concepts.pdf ''Concepts for Automating Systems Integration''] NIST 2003.</ref>
Most complex system specifications are so extensive that no single individual can fully comprehend all aspects of the specifications. Furthermore, we all have different interests in a given system and different reasons for examining the [[system]]'s [[specification]]s. A [[business]] executive will ask different questions of a system make-up than would a system implementer. The concept of viewpoints framework, therefore, is to provide separate viewpoints into the specification of a given complex system. These viewpoints each satisfy an audience with interest in a particular set of aspects of the system. Associated with each viewpoint is a viewpoint language
that optimizes the vocabulary and presentation for the audience of that viewpoint.
=== Business process and data modelling ===
[[Information visualisation|Graphical representation]] of the current state of information provides a very effective means for presenting information to both users and system [[developer]]s.
[[Image:Process and data modeling.jpg|thumb|360px|example of the interaction between business process and data models.<ref name="SS93"/>]]
* A [[business model]] illustrates the functions associated with a process that are performance and the organizations that perform these functions. By depicting activities and information flows, a foundation is created to visualize, define, understand, and validate the nature of a process.
* A [[data model]] provides the details of information to be stored, and is of primary use when the final product is the generation of computer [[software code]] for an application or the preparation of a functional
specification to aid a computer software make-or-buy decision. See the figure on the right for an example
of the interaction between business process and data models.<ref name="SS93"> Paul R. Smith & Richard Sarfaty (1993). [http://www.osti.gov/energycitations/servlets/purl/10160331-YhIRrY/ Creating a strategic plan for configuration management using Computer Aided Software Engineering (CASE) tools.] Paper For 1993 National DOE/Contractors and Facilities CAD/CAE User's Group.</ref>
Usually, a model is created after conducting an interview, referred to as [[business analysis]]. The interview consists of a facilitator asking a series of questions designed to extract required information that describes a process. The interviewer is called a facilitator to emphasize that it is the participants who provide the information. The facilitator should have some knowledge of the process of interest, but this is not as important as having a structured methodology by which the questions are asked of the process expert. The methodology is
important because usually a team of facilitators is collecting information cross the facility and the results of the information from all the interviewers must fit together once completed.<ref name="SS93"/>
The models are developed as defining either the current state of the process, in which case the final product is called the "as-is" snapshot model, or a collection of ideas of what the process should contain, resulting in a "what-can-be" model. Generation of process and data models can be used to determine if the existing processes and information systems are sound and only need minor modifications or enhancements, or if reengineering is required as corrective action. The creation of business models is more than a way to view or automate your information process analysis can be used to fundamentally reshape the way your business or organization conducts its operations.<ref name="SS93"/>
=== Computer-aided Software Engineering ===
[[Computer-Aided Software Engineering]] (CASE), in the field [[software engineering]] is the scientific application of a set of tools and methods to a [[software]] which results in high-quality, defect-free, and maintainable software products.<ref>Kuhn, D.L (1989). "Selecting and effectively using a computer aided software engineering tool". Annual Westinghouse computer symposium; 6-7 Nov 1989; Pittsburgh, PA (USA); DOE Project.</ref> It also refers to methods for the development of [[information system]]s together with automated tools that can be used in the [[software development process]]. <ref>P.Loucopoulus and V. Karakostas. ''System Requirement Engineering''.</ref> The term "Computer-aided software engineering" (CASE) can refer to the [[software]] used for the automated development of [[systems software]], i.e., computer code. The CASE functions include analysis, design, and programming. CASE tools automate methods for designing, documenting, and producing structured computer code in the desired [[programming language]].<ref>[http://www.its.bldrdoc.gov/projects/devglossary/_case.html CASE] definition In: ''[http://www.its.bldrdoc.gov/projects/devglossary/ Telecom Glossary 2000]. Retrieved 26 Oct 2008.''</ref>
Two key ideas of Computer-aided Software System Engineering (CASE) are:<ref>K. Robinson (1992). ''Putting the Software Engineering into CASE''. New York : John Wiley and Sons Inc.</ref>
* the harboring of computer assistance in [[software development]] and or [[software maintenance]] processes, and
* An engineering approach to the software development and or maintenance.
Some typical CASE tools are [[Configuration management]] tools, [[Data modeling]] tools, [[Model transformation]] tools, [[Refactoring]] tools, [[Source code generation]] tools, and [[Unified Modeling Language]].
=== Integrated development environment ===
[[Image:Anjuta-2.0.0-2.png|thumb|360px|[[Anjuta]], a C and C++ IDE for the GNOME environment]]
An [[integrated development environment]] (IDE) also known as ''integrated design environment'' or ''integrated debugging environment'' is a [[software application]] that provides comprehensive facilities to [[computer programmer]]s for software development. An IDE normally consists of a:
* [[source code editor]],
* [[compiler]] and/or [[interpreter (computing)|interpreter]],
* [[build automation]] tools, and
* [[debugger]] (usually).
IDEs are designed to maximize programmer productivity by providing tightly-knit components with similar [[user interface]]s. Typically an IDE is dedicated to a specific [[programming language]], so as to provide a feature set which most closely matches the [[programming paradigm]]s of the language.
=== Modeling language ===
A [[modeling language]] is any [[artificial language]] that can be used to express [[information]] or [[knowledge]] or [[system]]s in a [[structure]] that is defined by a consistent set of rules. The rules are used for interpretation of the meaning of components in the structure. A modeling language can be graphical or textual.<ref> Xiao He (2007). "A metamodel for the notation of graphical modeling languages". In: ''Computer Software and Applications Conference, 2007. COMPSAC 2007 - Vol. 1. 31st Annual International'', Volume 1, Issue , 24-27 July 2007, pp 219-224.</ref> Graphical modeling languages use a [[diagramming technique|diagram techniques]] with named symbols that represent concepts and lines that connect the symbols and that represent relationships and various other graphical annotation to represent constraints. Textual modeling languages typically use standardised keywords accompanied by parameters to make computer-interpretable expressions.
Example of graphical modelling languages in the field of software engineering are:
* [[Business Process Modeling Notation]] (BPMN, and the [[XML]] form BPML) is an example of a [[Process Modeling]] language.
* [[EXPRESS (data modeling language)|EXPRESS]] and EXPRESS-G (ISO 10303-11) is an international standard general-purpose [[data modeling]] language.
* [[Extended Enterprise Modeling Language]] (EEML) is commonly used for business process modeling across a number of layers.
* [[Flowchart]] is a schematic representation of an algorithm or a stepwise process,
* [[Fundamental Modeling Concepts]] (FMC) modeling language for software-intensive systems.
* [[IDEF]] is a family of modeling languages, the most notable of which include [[IDEF0]] for functional modeling, [[IDEF1X]] for information modeling, and [[IDEF5]] for modeling ontologies.
* [[Lepus3|LePUS3]] is an [[object-oriented]] visual Design Description Language and a [[formal specification]] language that is suitable primarily for modelling large object-oriented ([[Java (programming language)|Java]], [[C++]], [[C Sharp (programming language)|C#]]) programs and [[design patterns]].
* [[Specification and Description Language]](SDL) is a specification language targeted at the unambiguous specification and description of the behaviour of reactive and distributed systems.
* [[Unified Modeling Language]] (UML) is a [[general-purpose modeling]] language that is an industry standard for specifying software-intensive systems. UML 2.0, the current version, supports thirteen different diagram techniques, and has widespread tool support.
Not all modeling languages are executable, and for those that are, the use of them doesn't necessarily mean that programmers are no longer required. On the contrary, executable modeling languages are intended to amplify the productivity of skilled programmers, so that they can address more challenging problems, such as [[parallel computing]] and [[distributed system]]s.
=== Programming paradigm ===
A [[programming paradigm]] is a fundamental style of [[computer programming]], in contrast to a software engineering methodology, which is a style of solving specific [[software engineering]] problems. Paradigms differ in the concepts and abstractions used to represent the elements of a program (such as objects, functions, variables, constraints...) and the steps that compose a computation (assignation, evaluation, continuations, data flows...).
A [[programming language]] can support [[Multi-paradigm programming language|multiple paradigms]]. For example programs written in [[C++]] or [[Object Pascal]] can be purely [[procedural programming|procedural]], or purely [[object-oriented programming|object-oriented]], or contain elements of both paradigms. Software designers and programmers decide how to use those paradigm elements. In [[object-oriented programming]], programmers can think of a program as a collection of interacting objects, while in [[functional programming]] a program can be thought of as a sequence of stateless function evaluations. When programming computers or systems with many processors, [[process-oriented programming]] allows programmers to think about applications as sets of concurrent processes acting upon logically shared [[data structures]].
Just as different groups in [[software engineering]] advocate different ''methodologies'', different [[programming languages]] advocate different ''programming paradigms''. Some languages are designed to support one particular paradigm ([[Smalltalk]] supports object-oriented programming, [[Haskell (programming language)|Haskell]] supports functional programming), while other programming languages support multiple paradigms (such as [[Object Pascal]], [[C++]], [[C Sharp (programming language)|C#]], [[Visual Basic]], [[Common Lisp]], [[Scheme (programming language)|Scheme]], [[Python (programming language)|Python]], [[Ruby (programming language)|Ruby]] and [[Oz programming language|Oz]]).
Many programming paradigms are as well known for what techniques they ''forbid'' as for what they enable. For instance, pure functional programming disallows the use of [[Side-effect (computer science)|side-effects]]; [[structured programming]] disallows the use of the [[GOTO|goto]] statement. Partly for this reason, new paradigms are often regarded as doctrinaire or overly rigid by those accustomed to earlier styles. {{Fact|date=January 2008}} Avoiding certain techniques can make it easier to prove theorems about a program's correctness—or simply to understand its behavior.
=== Software framework ===
A [[software framework]] is a re-usable design for a software system or subsystem. A software framework may include support programs, code [[Library (computer science)|libraries]], a [[scripting language]], or other [[software]] to help develop and ''glue together'' the different components of a software project. Various parts of the framework may be exposed through an [[Application programming interface|API]].
.
=== Software development process ===
A [[Software development process]] is a structure imposed on the development of a software product. Synonyms include [[Software Lifecycle Processes|software life cycle]] and ''software process''. There are several [[Software development process#Process models|models]] for such processes, each describing approaches to a variety of [[Software development process#Process models|tasks or activities]] that take place during the process.
A largely growing body of [[software development]] organizations implement process methodologies. Many of them are in the [[defense industry]], which in the [[U.S.]] requires a rating based on '[[process model]]s' to obtain contracts. The international standard for describing the method of selecting, implementing and monitoring the life cycle for software is [[ISO 12207]].
A decades-long goal has been to find repeatable, predictable processes that improve productivity and quality. Some try to systematize or formalize the seemingly unruly task of writing software. Others apply project management techniques to writing software. Without project management, software projects can easily be delivered late or over budget. With large numbers of software projects not meeting their expectations in terms of functionality, cost, or delivery schedule, effective project management appears to be lacking.
== See also ==
<!-- Please don't list individual Software development methodologies here. These should be integrated in the text itself or in the current articles mentioned -->
;Lists
* [[List of software engineering topics]]
* [[List of software development philosophies]]
;Related topics
* [[Domain-specific modeling]]
* [[Lightweight methodology]]
* [[Object modeling language]]<!-- This seems close related to object oriented programming. There seems to be only two images representing this field.-->
* [[Structured programming]]
== References ==
{{reflist}}
== External links ==
{{Commonscat|Software development methodology}}
* [http://www.cms.hhs.gov/SystemLifecycleFramework/Downloads/SelectingDevelopmentApproach.pdf Selecting a development approach] at cms.hhs.gov.
* [http://www.techbookreport.com/SoftwareIndex.html Software Methodologies Book Reviews] An extensive set of book reviews related to software methodologies and processes
{{Software Engineering}}
[[Category:Software engineering]]
[[Category:Software development]]
[[Category:Software development process]]
[[Category:Software development philosophies| ]]
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