In
software development
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development invol ...
, agile (sometimes written Agile) practices include requirements discovery and solutions improvement through the collaborative effort of
self-organizing
Self-organization, also called spontaneous order in the social sciences, is a process where some form of overall order arises from local interactions between parts of an initially disordered system. The process can be spontaneous when suff ...
and
cross-functional teams with their
customer(s)/
end user(s),
adaptive planning, evolutionary development, early delivery,
continual improvement
A continual improvement process, also often called a continuous improvement process (abbreviated as CIP or CI), is an ongoing effort to improve products, services, or processes. These efforts can seek "incremental" improvement over time or "breakth ...
, and flexible responses to changes in requirements, capacity, and understanding of the problems to be solved.
Popularized in the 2001 ''Manifesto for Agile Software Development'',
these values and principles were derived from and underpin a broad range of
software development frameworks, including
Scrum
Scrum may refer to:
Sport
* Scrum (rugby), a method of restarting play in rugby union and rugby league
** Scrum (rugby union), scrum in rugby union
* Scrum, an offensive melee formation in Japanese game Bo-taoshi
Media and popular culture
* M ...
and
Kanban
Kanban (Japanese: カンバン and Chinese: 看板, meaning signboard or billboard) is a scheduling system for lean manufacturing (also called just-in-time manufacturing, abbreviated JIT). Taiichi Ohno, an industrial engineer at Toyota, develope ...
.
While there is much
anecdotal evidence
Anecdotal evidence is evidence based only on personal observation, collected in a casual or non-systematic manner. The term is sometimes used in a legal context to describe certain kinds of testimony which are uncorroborated by objective, independ ...
that adopting agile practices and values improves the effectiveness of software professionals, teams and organizations, the empirical evidence is mixed and hard to find.
History
Iterative and incremental software development methods can be traced back as early as 1957,
Gerald M. Weinberg
Gerald Marvin Weinberg (October 27, 1933 – August 7, 2018) was an American computer scientist, author and teacher of the psychology and anthropology of computer software development. His most well-known books are ''The Psychology of Computer ...
, as quoted in "We were doing incremental development as early as 1957 in Los Angeles, under the direction of Bernie Dimsdale at IBM's Service Bureau Corporation. He was a colleague of John von Neumann
John von Neumann (; hu, Neumann János Lajos, ; December 28, 1903 – February 8, 1957) was a Hungarian-American mathematician, physicist, computer scientist, engineer and polymath. He was regarded as having perhaps the widest cove ...
, so perhaps he learned it there, or assumed it as totally natural. I do remember Herb Jacobs (primarily, though we all participated) developing a large simulation for Motorola, where the technique used was, as far as I can tell ... All of us, as far as I can remember, thought waterfalling of a huge project was rather stupid, or at least ignorant of the realities. I think what the waterfall description did for us was make us realize that we were doing something else, something unnamed except for 'software development.'" with evolutionary project management
and
adaptive software development Adaptive software development (ASD) is a software development process that grew out of the work by Jim Highsmith and Sam Bayer on rapid application development (RAD). It embodies the principle that continuous adaptation of the process to the work a ...
emerging in the early 1970s.
During the 1990s, a number of ''lightweight'' software development methods evolved in reaction to the prevailing ''heavyweight'' methods (often referred to collectively as
''waterfall'') that critics described as overly regulated, planned, and
micromanaged. These lightweight methods included:
rapid application development
Rapid application development (RAD), also called rapid application building (RAB), is both a general term for adaptive software development approaches, and the name for James Martin's method of rapid development. In general, RAD approaches to ...
(RAD), from 1991; the
unified process
The Unified Software Development Process or Unified Process is an iterative and incremental software development process framework. The best-known and extensively documented refinement of the Unified Process is the Rational Unified Process (RU ...
(UP) and
dynamic systems development method
Dynamic systems development method (DSDM) is an agile project delivery framework, initially used as a software development method. First released in 1994, DSDM originally sought to provide some discipline to the rapid application development (R ...
(DSDM), both from 1994;
Scrum
Scrum may refer to:
Sport
* Scrum (rugby), a method of restarting play in rugby union and rugby league
** Scrum (rugby union), scrum in rugby union
* Scrum, an offensive melee formation in Japanese game Bo-taoshi
Media and popular culture
* M ...
, from 1995; Crystal Clear and
extreme programming
Extreme programming (XP) is a software development methodology intended to improve software quality and responsiveness to changing customer requirements. As a type of agile software development,"Human Centred Technology Workshop 2006 ", 2006, PD ...
(XP), both from 1996; and
feature-driven development
Feature-driven development (FDD) is an iterative and incremental software development process. It is a lightweight or Agile method for developing software. FDD blends a number of industry-recognized best practices into a cohesive whole. These p ...
(FDD), from 1997. Although these all originated before the publication of the ''Agile Manifesto'', they are now collectively referred to as agile software development methods.
Already since 1991 similar changes had been underway in manufacturing and
management thinking derived from
Lean management
Lean project management is the application of lean concepts such as lean construction, lean manufacturing and lean thinking to project management.
Lean project management has many ideas in common with other lean concepts; however, the main prin ...
.
In 2001, seventeen software developers met at a resort in
Snowbird
Snowbird is a common name for the dark-eyed junco (''Junco hyemalis'').
Snowbird may also refer to:
Places
*Snowbird, Utah, an unincorporated area and associated ski resort
*Snowbird Lake, a lake in the Northwest Territories, Canada
*Snowbird ...
,
Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to it ...
to discuss lightweight development methods. They were:
Kent Beck
Kent Beck (born 1961) is an American software engineer and the creator of extreme programming, a software development methodology that eschews rigid formal specification for a collaborative and iterative design process. Beck was one of the 17 ori ...
(Extreme Programming),
Ward Cunningham (Extreme Programming),
Dave Thomas Dave may refer to:
Film, television, and theater
* Dave (film), ''Dave'' (film), a 1993 film starring Kevin Kline and Sigourney Weaver
* Dave (musical), ''Dave'' (musical), a 2018 stage musical adaptation of the film
* Dave (TV channel), a digital ...
(
PragProg, Ruby),
Jeff Sutherland
Jeff Sutherland (born June 20, 1941) is one of the creators of the Scrum, a framework for product management. Together with Ken Schwaber, he presented Scrum at OOPSLA'95. Sutherland contributed to the creation of the Agile Manifesto in 2001. Along ...
(Scrum),
Ken Schwaber
Ken Schwaber (born 1945 in Wheaton, Illinois) is a software developer, product manager and industry consultant. He worked with Jeff Sutherland to formulate the initial versions of the Scrum framework and to present Scrum as a formal process ...
(Scrum),
Jim Highsmith
James A. Highsmith III (born 1945) is an American software engineer and author of books in the field of software development methodology. He is the creator of Adaptive Software Development, described in his 1999 book "Adaptive Software Development" ...
(Adaptive Software Development),
Alistair Cockburn
Alistair Cockburn ( ) is an American computer scientist, known as one of the initiators of the agile movement in software development. He cosigned (with 17 others) the Manifesto for Agile Software Development.
Life and career
Cockburn starte ...
(Crystal),
Robert C. Martin
Robert Cecil Martin (born 5 December 1952), colloquially called "Uncle Bob", is an American software engineer, instructor, and best-selling author. He is most recognized for developing many software design principles and for being a founder of t ...
(
SOLID
Solid is one of the State of matter#Four fundamental states, four fundamental states of matter (the others being liquid, gas, and Plasma (physics), plasma). The molecules in a solid are closely packed together and contain the least amount o ...
),
Mike Beedle
Mike (Miguel) Beedle was an American theoretical physicist turned software engineer who was a co-author of the Agile Manifesto.
He was the co-author of the first book and earliest papers about Scrum. Later he coined the term "Enterprise Scrum," ...
(Scrum),
Arie van Bennekum,
Martin Fowler (OOAD and UML), James Grenning,
Andrew Hunt (PragProg, Ruby),
Ron Jeffries
Ron Jeffries (born December 26, 1939) is one of the three founders of the Extreme Programming (XP) software development methodology circa 1996, along with Kent Beck and Ward Cunningham. He was from 1996, an XP coach on the Chrysler Comprehensiv ...
(Extreme Programming),
Jon Kern, Brian Marick (Ruby, TDD), and
Steve Mellor (OOA). Together they published the ''Manifesto for Agile Software Development''.
In 2005, a group headed by Cockburn and Highsmith wrote an addendum of
project management
Project management is the process of leading the work of a team to achieve all project goals within the given constraints. This information is usually described in project documentation, created at the beginning of the development process. Th ...
principles, the PM Declaration of Interdependence, to guide software project management according to agile software development methods.
In 2009, a group working with Martin wrote an extension of
software development
Software development is the process of conceiving, specifying, designing, programming, documenting, testing, and bug fixing involved in creating and maintaining applications, frameworks, or other software components. Software development invol ...
principles, the
Software Craftsmanship Manifesto, to guide agile software development according to
professional
A professional is a member of a profession or any person who works in a specified professional activity. The term also describes the standards of education and training that prepare members of the profession with the particular knowledge and skil ...
conduct and mastery.
In 2011, the Agile Alliance created the ''Guide to Agile Practices'' (renamed the ''Agile Glossary'' in 2016), an evolving
open-source
Open source is source code that is made freely available for possible modification and redistribution. Products include permission to use the source code, design documents, or content of the product. The open-source model is a decentralized sof ...
compendium of the working definitions of agile practices, terms, and elements, along with interpretations and experience guidelines from the worldwide community of agile practitioners.
''The Manifesto for Agile Software Development''
Agile software development values
Based on their combined experience of developing software and helping others do that, the authors of the manifesto declared that they valued:
*
*
*
*
That is to say, while both sides have value and the items on the right should be considered, the authors felt that the items on the left should have more influence on how people approach their work.
As
Scott Ambler
Scott W. Ambler (born 1966) is a Canadian software engineer, consultant and author. He is an author of books about the Disciplined Agile Delivery toolkit, the Unified process, Agile software development, the Unified Modeling Language, and Capabili ...
explained:
[
]
* Tools and processes are important, but it is more important to have competent people working together effectively.
*Good documentation is useful in helping people to understand how the software is built and how to use it, but the main point of development is to create software, not documentation.
*A contract is important but is no substitute for working closely with customers to discover what they need.
*A project plan is important, but it must not be too rigid to accommodate changes in technology or the environment, stakeholders' priorities, and people's understanding of the problem and its solution.
Some of the authors formed the Agile Alliance, a non-profit organization that promotes software development according to the manifesto's values and principles. Introducing the manifesto on behalf of the Agile Alliance,
Jim Highsmith
James A. Highsmith III (born 1945) is an American software engineer and author of books in the field of software development methodology. He is the creator of Adaptive Software Development, described in his 1999 book "Adaptive Software Development" ...
said,
Agile software development principles
The ''Manifesto for Agile Software Development'' is based on twelve principles:
[
]
# Customer satisfaction by early and continuous delivery of valuable software.
# Welcome changing requirements, even in late development.
# Deliver working software frequently (weeks rather than months).
# Close, daily cooperation between business people and developers.
# Projects are built around motivated individuals, who should be trusted.
# Face-to-face conversation is the best form of communication (co-location).
# Working software is the primary measure of progress.
# Sustainable development, able to maintain a constant pace.
# Continuous attention to technical excellence and good design.
# Simplicity—the art of maximizing the amount of work done—is essential.
# Best
architectures
Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing buildings o ...
, requirements, and designs emerge from self-organizing teams.
# Regularly, the team reflects on how to become more effective, and adjusts accordingly.
Overview
Iterative, incremental, and evolutionary
Most agile development methods break product development work into small increments that minimize the amount of up-front planning and design. Iterations, or sprints, are short time frames (
timeboxes) that typically last from one to four weeks. Each iteration involves a
cross-functional team
A cross-functional team, also known as a multidisciplinary team or interdisciplinary team, is a group of people with different functional expertise working toward a common goal. It may include people from finance, marketing, operations, and human ...
working in all functions:
planning
Planning is the process of thinking regarding the activities required to achieve a desired goal. Planning is based on foresight, the fundamental capacity for mental time travel. The evolution of forethought, the capacity to think ahead, is consi ...
,
analysis
Analysis ( : analyses) is the process of breaking a complex topic or substance into smaller parts in order to gain a better understanding of it. The technique has been applied in the study of mathematics and logic since before Aristotle (38 ...
,
design
A design is a plan or specification for the construction of an object or system or for the implementation of an activity or process or the result of that plan or specification in the form of a prototype, product, or process. The verb ''to design'' ...
,
coding,
unit testing
In computer programming, unit testing is a software testing method by which individual units of source code—sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures&md ...
, and
acceptance testing
In engineering and its various subdisciplines, acceptance testing is a test conducted to determine if the requirements of a specification or contract are met. It may involve chemical tests, physical tests, or performance tests.
In systems en ...
. At the end of the iteration a working product is demonstrated to stakeholders. This minimizes overall risk and allows the product to adapt to changes quickly.
An iteration might not add enough functionality to warrant a market release, but the goal is to have an available release (with minimal
bugs) at the end of each iteration.
Through incremental development, products have room to "fail often and early" throughout each iterative phase instead of drastically on a final release date. Multiple iterations might be required to release a product or new features. Working software is the primary measure of progress.
A key advantage of agile approaches is speed to market and risk mitigation. Smaller increments are typically released to market, reducing the time and cost risks of engineering a product that doesn't meet user requirements.
Efficient and face-to-face communication
The 6th principle of the agile manifesto for software development states "The most efficient and effective method of conveying information to and within a development team is face-to-face conversation". The manifesto, written in 2001 when video conferencing was not widely used, states this in relation to the communication of information, not necessarily that a team should be co-located.
The principle of
co-location is that co-workers on the same team should be situated together to better establish the identity as a team and to improve communication. This enables
face-to-face interaction
Face-to-face interaction is social communication carried out without any mediating technology. It is defined as the mutual influence of individuals’ direct physical presence with their body language and verbal language. It is one of the basic ...
, ideally in front of a whiteboard, that reduces the cycle time typically taken when questions and answers are mediated through phone,
persistent chat Persistent Chat is a messaging concept for group chat software that consist of standing, topic-based chatrooms with an emphasis on real-time messaging, that preserve conversation history over time which is visible to both current and future particip ...
, wiki, or email. With the widespread adoption of remote working during the COVID-19 pandemic and changes to tooling, more studies have been conducted around co-location and distributed working which show that co-location is increasingly less relevant.
No matter which development method is followed, every team should include a
customer representative
A customer representative is an individual who has authority to represent a community that intends to purchase a product. The term is most often applied to a representative of a company, or proxy, who works closely with a producer or developer to c ...
(known as ''product owner'' in
Scrum
Scrum may refer to:
Sport
* Scrum (rugby), a method of restarting play in rugby union and rugby league
** Scrum (rugby union), scrum in rugby union
* Scrum, an offensive melee formation in Japanese game Bo-taoshi
Media and popular culture
* M ...
). This representative is agreed by stakeholders to act on their behalf and makes a personal commitment to being available for developers to answer questions throughout the iteration. At the end of each iteration, the
project stakeholder
Project stakeholders are persons or entities who have an interest in a given project. According to the Project Management Institute (PMI), the term ''project stakeholder'' refers to "an individual, group, or organization, who may affect, be affect ...
s together with the customer representative review progress and re-evaluate priorities with a view to optimizing the
return on investment
Return on investment (ROI) or return on costs (ROC) is a ratio between net income (over a period) and investment (costs resulting from an investment of some resources at a point in time). A high ROI means the investment's gains compare favourably ...
(ROI) and ensuring alignment with customer needs and company goals. The importance of stakeholder satisfaction, detailed by frequent interaction and review at the end of each phase, is why the approach is often denoted as a
customer-centered methodology.
In agile software development, an information radiator is a (normally large) physical display, board with
sticky note
A Post-it Note (or sticky note) is a small piece of paper with a re-adherable strip of glue on its back, made for temporarily attaching notes to documents and other surfaces. A low-tack pressure-sensitive adhesive allows the notes to be easil ...
s or similar, located prominently near the development team, where passers-by can see it. It presents an up-to-date summary of the product development status.
A
build light indicator
A build light indicator is a simple visual indicator used in Agile software development to inform a team of software developers about the current status of their project. The actual object used can vary from a pressure gauge to a lava lamp, but ...
may also be used to inform a team about the current status of their product development.
Very short feedback loop and adaptation cycle
A common characteristic in agile software development is the
daily stand-up (known as ''daily scrum'' in the Scrum framework). In a brief session (e.g., 15 minutes), team members review collectively how they are progressing toward their goal and agree whether they need to adapt their approach. To keep to the agreed time limit, teams often use simple coded questions (such as what they completed the previous day, what they aim to complete that day, and whether there are any impediments or risks to progress), and delay detailed discussions and problem resolution until after the stand-up.
Quality focus
Specific tools and techniques, such as
continuous integration, automated
unit testing
In computer programming, unit testing is a software testing method by which individual units of source code—sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures&md ...
,
pair programming
Pair programming is an software development technique in which two programmers work together at one workstation. One, the ''driver'', writes code while the other, the ''observer'' or ''navigator'', reviews each line of code as it is typed in. The ...
,
test-driven development
Test-driven development (TDD) is a software development process relying on software requirements being converted to test cases before software is fully developed, and tracking all software development by repeatedly testing the software against al ...
,
design patterns
''Design Patterns: Elements of Reusable Object-Oriented Software'' (1994) is a software engineering book describing software design patterns. The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword ...
,
behavior-driven development
In software engineering, behavior-driven development (BDD) is an agile software development process that encourages collaboration among developers, quality assurance experts, and customer representatives in a software project. It encourages teams ...
,
domain-driven design
Domain-driven design (DDD) is a major software design approach, focusing on modeling software to match a domain according to input from that domain's experts.
Under domain-driven design, the structure and language of software code (class name ...
,
code refactoring
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structur ...
and other techniques are often used to improve quality and enhance product development agility. This is predicated on designing and building quality in from the beginning and being able to demonstrate software for customers at any point, or at least at the end of every iteration.
Philosophy
Compared to traditional software engineering, agile software development mainly targets complex systems and product development with dynamic, non-deterministic and non-linear characteristics. Accurate estimates, stable plans, and predictions are often hard to get in early stages, and confidence in them is likely to be low. Agile practitioners will seek to reduce the ''leap-of-faith'' that is needed before any evidence of value can be obtained.
Requirements and design are held to be emergent. Big up-front specifications would probably cause a lot of waste in such cases, i.e., are not economically sound. These basic arguments and previous industry experiences, learned from years of successes and failures, have helped shape agile development's favor of adaptive, iterative and evolutionary development.
Adaptive vs. predictive
Development methods exist on a continuum from ''adaptive'' to ''predictive''.
[ Appendix A, pages 165–194] Agile software development methods lie on the ''adaptive'' side of this continuum. One key of adaptive development methods is a
''rolling wave'' approach to schedule planning, which identifies milestones but leaves flexibility in the path to reach them, and also allows for the milestones themselves to change.
''Adaptive'' methods focus on adapting quickly to changing realities. When the needs of a project change, an adaptive team changes as well. An adaptive team has difficulty describing exactly what will happen in the future. The further away a date is, the more vague an adaptive method is about what will happen on that date. An adaptive team cannot report exactly what tasks they will do next week, but only which features they plan for next month. When asked about a release six months from now, an adaptive team might be able to report only the mission statement for the release, or a statement of expected value vs. cost.
''Predictive'' methods, in contrast, focus on analysing and planning the future in detail and cater for known risks. In the extremes, a predictive team can report exactly what features and tasks are planned for the entire length of the development process. Predictive methods rely on effective early phase analysis and if this goes very wrong, the project may have difficulty changing direction. Predictive teams often institute a
change control board
In software development, projects and programs, a change control board (CCB) is a committee that consists of Subject Matter Experts (''SME'', e.g. software engineers, testing experts, etc.) and Managers (e.g. Quality Assurance managers), who decide ...
to ensure they consider only the most valuable changes.
Risk analysis can be used to choose between adaptive (''agile'' or ''value-driven'') and predictive (''plan-driven'') methods.
Barry Boehm
Barry William Boehm (May 16, 1935 – August 20, 2022) was an American software engineer, distinguished professor of computer science, industrial and systems engineering; the TRW Professor of Software Engineering; and founding director of the Cen ...
and
Richard Turner suggest that each side of the continuum has its own ''home ground'', as follows:
Agile vs. waterfall
One of the differences between agile software development methods and waterfall is the approach to quality and testing. In the
waterfall model
The waterfall model is a breakdown of project activities into linear sequential phases, meaning they are passed down onto each other, where each phase depends on the deliverables of the previous one and corresponds to a specialization of tasks. ...
, work moves through
software development lifecycle
In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software devel ...
(SDLC) phases—with one phase being completed before another can start—hence the ''testing phase'' is separate and follows a ''build phase''. In agile software development, however, testing is completed in the same iteration as programming.
Because testing is done in every iteration—which develops a small piece of the software—users can frequently use those new pieces of software and validate the value. After the users know the real value of the updated piece of software, they can make better decisions about the software's future. Having a value retrospective and software re-planning session in each iteration—
Scrum
Scrum may refer to:
Sport
* Scrum (rugby), a method of restarting play in rugby union and rugby league
** Scrum (rugby union), scrum in rugby union
* Scrum, an offensive melee formation in Japanese game Bo-taoshi
Media and popular culture
* M ...
typically has iterations of just two weeks—helps the team continuously adapt its plans so as to maximize the value it delivers. This follows a pattern similar to the
plan-do-check-act (PDCA) cycle, as the work is ''planned'', ''done'', ''checked'' (in the review and retrospective), and any changes agreed are ''acted'' upon.
This iterative approach supports a ''product'' rather than a ''project'' mindset. This provides greater flexibility throughout the development process; whereas on projects the requirements are defined and locked down from the very beginning, making it difficult to change them later. Iterative product development allows the software to evolve in response to changes in business environment or market requirements.
Code vs. documentation
In a letter to ''
IEEE Computer
''Computer'' is an IEEE Computer Society practitioner-oriented magazine issued to all members of the society. It contains peer-reviewed articles, regular columns, and interviews on current computing-related issues. ''Computer'' provides informatio ...
'', Steven Rakitin expressed cynicism about agile software development, calling it "''yet another attempt to undermine the discipline of software engineering''" and translating "''working software over comprehensive documentation''" as "''we want to spend all our time coding. Remember, real programmers don't write documentation''."
This is disputed by proponents of agile software development, who state that developers should write documentation if that is the best way to achieve the relevant goals, but that there are often better ways to achieve those goals than writing static documentation.
Scott Ambler
Scott W. Ambler (born 1966) is a Canadian software engineer, consultant and author. He is an author of books about the Disciplined Agile Delivery toolkit, the Unified process, Agile software development, the Unified Modeling Language, and Capabili ...
states that documentation should be "just barely good enough" (JBGE), that too much or comprehensive documentation would usually cause waste, and developers rarely trust detailed documentation because it's usually out of sync with code,
while too little documentation may also cause problems for maintenance, communication, learning and knowledge sharing.
Alistair Cockburn
Alistair Cockburn ( ) is an American computer scientist, known as one of the initiators of the agile movement in software development. He cosigned (with 17 others) the Manifesto for Agile Software Development.
Life and career
Cockburn starte ...
wrote of the ''Crystal Clear'' method:
Agile software development methods
![Unified_Process_Model_for_Iterative_Development](https://upload.wikimedia.org/wikipedia/commons/c/c2/Unified_Process_Model_for_Iterative_Development.svg)
Agile software development methods support a broad range of the
software development life cycle
In software engineering, a software development process is a process of dividing software development work into smaller, parallel, or sequential steps or sub-processes to improve design, product management. It is also known as a software devel ...
.
Some methods focus on the practices (e.g.,
XP,
pragmatic programming, agile modeling), while some focus on managing the flow of work (e.g., Scrum, Kanban). Some support activities for requirements specification and development (e.g.,
FDD), while some seek to cover the full development life cycle (e.g.,
DSDM,
RUP).
Notable agile software development frameworks include:
Agile software development practices
Agile software development is supported by a number of concrete practices, covering areas like requirements, design, modeling, coding, testing, planning, risk management, process, quality, etc. Some notable agile software development practices include:
Method tailoring
In the literature, different terms refer to the notion of method adaptation, including 'method tailoring', 'method fragment adaptation' and 'situational method engineering'. Method tailoring is defined as:
Situation-appropriateness should be considered as a distinguishing characteristic between agile methods and more plan-driven software development methods, with agile methods allowing product development teams to adapt working practices according to the needs of individual products.
Potentially, most agile methods could be suitable for method tailoring,
such as
DSDM tailored in a
CMM context.
[Abrahamsson, P., Warsta, J., Siponen, M.T., & Ronkainen, J. (2003). New Directions on Agile Methods: A Comparative Analysis. ''Proceedings of ICSE'03'', 244-254] and XP tailored with the ''Rule Description Practices'' (RDP) technique. Not all agile proponents agree, however, with Schwaber noting "that is how we got into trouble in the first place, thinking that the problem was not having a perfect methodology. Efforts
houldcenter on the changes
eededin the enterprise". Bas Vodde reinforced this viewpoint, suggesting that unlike traditional, large methodologies that require you to pick and choose elements, Scrum provides the basics on top of which you add additional elements to localize and contextualize its use. Practitioners seldom use
system development methods, or agile methods specifically, by the book, often choosing to omit or tailor some of the practices of a method in order to create an in-house method.
In practice, methods can be tailored using various tools. Generic process modeling languages such as
Unified Modeling Language
The Unified Modeling Language (UML) is a general-purpose, developmental modeling language in the field of software engineering that is intended to provide a standard way to visualize the design of a system.
The creation of UML was originally m ...
can be used to tailor software development methods. However, dedicated tools for method engineering such as the Essence Theory of Software Engineering of
SEMAT
Semat was an Ancient Egyptian Queen, who was a wife of the King Den. She was buried near him in Abydos.
Very little is known about Semat besides a stela discovered near Den's tomb in Abydos. She held the titles of
Both of these titles were a ...
also exist.
Large-scale, offshore and distributed
Agile software development has been widely seen as highly suited to certain types of environments, including small teams of experts working on
greenfield project
In many disciplines, a greenfield project is one that lacks constraints imposed by prior work. The analogy is to that of construction on greenfield land where there is no need to work within the constraints of existing buildings or infrastructure ...
s,
and the challenges and limitations encountered in the adoption of agile software development methods in a large organization with
legacy infrastructure are well-documented and understood.
In response, a range of strategies and patterns has evolved for overcoming challenges with large-scale development efforts (>20 developers)
[Schaaf, R.J. (2007). Agility X]
Systems and Software Technology Conference 2007
, Tampa, FL or distributed (non-colocated) development teams,
amongst other challenges; and there are now several recognized frameworks that seek to mitigate or avoid these challenges.
There are many conflicting viewpoints on whether all of these are effective or indeed fit the definition of agile development, and this remains an active and ongoing area of research.
[W. Scott Ambler (2006]
Supersize Me
in Dr. Dobb's Journal, 15 February 2006.[Agile Processes Workshop II Managing Multiple Concurrent Agile Projects. Washington: OOPSLA 2002]
When agile software development is applied in a distributed setting (with teams dispersed across multiple business locations), it is commonly referred to as
distributed agile software development. The goal is to leverage the unique benefits offered by each approach. Distributed development allows organizations to build software by strategically setting up teams in different parts of the globe, virtually building software round-the-clock (more commonly referred to as follow-the-sun model). On the other hand, agile development provides increased transparency, continuous feedback, and more flexibility when responding to changes.
Regulated domains
Agile software development methods were initially seen as best suitable for non-critical product developments, thereby excluded from use in regulated domains such as
medical device
A medical device is any device intended to be used for medical purposes. Significant potential for hazards are inherent when using a device for medical purposes and thus medical devices must be proved safe and effective with reasonable assura ...
s, pharmaceutical, financial, nuclear systems, automotive, and avionics sectors, etc. However, in the last several years, there have been several initiatives for the adaptation of agile methods for these domains.
There are numerous standards that may apply in regulated domains, including
ISO 26262
ISO 26262, titled "Road vehicles – Functional safety", is an international standard for functional safety of electrical and/or electronic systems that are installed in serial production road vehicles (excluding mopeds), defined by the Interna ...
,
ISO 9000
The ISO 9000 family is a set of five quality management systems (QMS) standards that help organizations ensure they meet customer and other stakeholder needs within statutory and regulatory requirements related to a product or service. ISO 90 ...
,
ISO 9001
The ISO 9000 family is a set of five quality management systems (QMS) standards that help organizations ensure they meet customer and other stakeholder needs within statutory and regulatory requirements related to a product or service. ISO 90 ...
, and
ISO/IEC 15504
ISO/IEC 15504 ''Information technology – Process assessment'', also termed Software Process Improvement and Capability Determination (SPICE), is a set of technical standards documents for the computer software development process and related bus ...
.
A number of key concerns are of particular importance in regulated domains:
*
Quality assurance
Quality assurance (QA) is the term used in both manufacturing and service industries to describe the systematic efforts taken to ensure that the product(s) delivered to customer(s) meet with the contractual and other agreed upon performance, design ...
(QA): Systematic and inherent quality management underpinning a controlled professional process and reliability and correctness of product.
* Safety and security: Formal planning and risk management to mitigate safety risks for users and securely protecting users from unintentional and malicious misuse.
*
Traceability Traceability is the capability to trace something. In some cases, it is interpreted as the ability to verify the history, location, or application of an item by means of documented recorded identification.
Other common definitions include the capab ...
: Documentation providing auditable evidence of regulatory compliance and facilitating traceability and investigation of problems.
*
Verification and validation
Verification and validation (also abbreviated as V&V) are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfills its intended purpose. These are ...
(V&V): Embedded throughout the software development process (e.g. user requirements specification, functional specification, design specification, code review, unit tests, integration tests, system tests).
Experience and adoption
Although agile software development methods can be used with any programming paradigm or language in practice, they were originally closely associated with object-oriented environments such as Smalltalk, Lisp and later Java, C#. The initial adopters of agile methods were usually small to medium-sized teams working on unprecedented systems with requirements that were difficult to finalize and likely to change as the system was being developed. This section describes common problems that organizations encounter when they try to adopt agile software development methods as well as various techniques to measure the quality and performance of agile teams.
Measuring agility
Internal assessments
The ''Agility measurement index'', amongst others, rates developments against five dimensions of product development (duration, risk, novelty, effort, and interaction). Other techniques are based on measurable goals and one study suggests that
velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
can be used as a metric of agility. There are also agile self-assessments to determine whether a team is using agile software development practices (Nokia test, Karlskrona test, 42 points test).
Public surveys
One of the early studies reporting gains in quality, productivity, and business satisfaction by using agile software developments methods was a survey conducted by Shine Technologies from November 2002 to January 2003.
A similar survey, the ''State of Agile'', is conducted every year starting in 2006 with thousands of participants from around the software development community. This tracks trends on the perceived benefits of agility, lessons learned, and good practices. Each survey has reported increasing numbers saying that agile software development helps them deliver software faster; improves their ability to manage changing customer priorities; and increases their productivity. Surveys have also consistently shown better results with agile product development methods compared to classical project management. In balance, there are reports that some feel that agile development methods are still too young to enable extensive academic research of their success.
Common agile software development pitfalls
Organizations and teams implementing agile software development often face difficulties transitioning from more traditional methods such as
waterfall development
The waterfall model is a breakdown of project activities into linear sequential phases, meaning they are passed down onto each other, where each phase depends on the deliverables of the previous one and corresponds to a specialization of tasks. ...
, such as teams having an agile process forced on them.
These are often termed ''agile anti-patterns'' or more commonly ''agile smells''. Below are some common examples:
Lack of overall product design
A goal of agile software development is to focus more on producing working software and less on documentation. This is in contrast to waterfall models where the process is often highly controlled and minor changes to the system require significant revision of supporting documentation. However, this does not justify completely doing without any analysis or design at all. Failure to pay attention to design can cause a team to proceed rapidly at first but then to have significant rework required as they attempt to scale up the system. One of the key features of agile software development is that it is iterative. When done correctly design emerges as the system is developed and commonalities and opportunities for re-use are discovered.
Adding stories to an iteration in progress
In agile software development, ''stories'' (similar to
use case
In software and systems engineering, the phrase use case is a polyseme with two senses:
# A usage scenario for a piece of software; often used in the plural to suggest situations where a piece of software may be useful.
# A potential scenario ...
descriptions) are typically used to define requirements and an ''iteration'' is a short period of time during which the team commits to specific goals. Adding stories to an iteration in progress is detrimental to a good flow of work. These should be added to the product backlog and prioritized for a subsequent iteration or in rare cases the iteration could be cancelled.
This does not mean that a story cannot expand. Teams must deal with new information, which may produce additional tasks for a story. If the new information prevents the story from being completed during the iteration, then it should be carried over to a subsequent iteration. However, it should be prioritized against all remaining stories, as the new information may have changed the story's original priority.
Lack of sponsor support
Agile software development is often implemented as a grassroots effort in organizations by software development teams trying to optimize their development processes and ensure consistency in the software development life cycle. By not having sponsor support, teams may face difficulties and resistance from business partners, other development teams and management. Additionally, they may suffer without appropriate funding and resources. This increases the likelihood of failure.
Insufficient training
A survey performed by VersionOne found respondents cited insufficient training as the most significant cause for failed agile implementations Teams have fallen into the trap of assuming the reduced processes of agile software development compared to other approaches such as waterfall means that there are no actual rules for agile software development.
Product owner role is not properly filled
The
product owner
Scrum is a framework for project management with an initial emphasis on software development, although it has been used in other fields including research, sales, marketing and advanced technologies. It is designed for teams of ten or fewer m ...
is responsible for representing the business in the development activity and is often the most demanding role.
A common mistake is to have the product owner role filled by someone from the development team. This requires the team to make its own decisions on prioritization without real feedback from the business. They try to solve business issues internally or delay work as they reach outside the team for direction. This often leads to distraction and a breakdown in collaboration.
Teams are not focused
Agile software development requires teams to meet product commitments, which means they should focus on work for only that product. However, team members who appear to have spare capacity are often expected to take on other work, which makes it difficult for them to help complete the work to which their team had committed.
Excessive preparation/planning
Teams may fall into the trap of spending too much time preparing or planning. This is a common trap for teams less familiar with agile software development where the teams feel obliged to have a complete understanding and specification of all stories. Teams should be prepared to move forward with only those stories in which they have confidence, then during the iteration continue to discover and prepare work for subsequent iterations (often referred to as
backlog refinement or grooming).
Problem-solving in the daily standup
A daily standup should be a focused, timely meeting where all team members disseminate information. If problem-solving occurs, it often can involve only certain team members and potentially is not the best use of the entire team's time. If during the daily standup the team starts diving into problem-solving, it should be set aside until a sub-team can discuss, usually immediately after the standup completes.
Assigning tasks
One of the intended benefits of agile software development is to empower the team to make choices, as they are closest to the problem. Additionally, they should make choices as close to implementation as possible, to use more timely information in the decision. If team members are assigned tasks by others or too early in the process, the benefits of localized and timely decision making can be lost.
Being assigned work also constrains team members into certain roles (for example, team member A must always do the database work), which limits opportunities for cross-training.
Team members themselves can choose to take on tasks that stretch their abilities and provide cross-training opportunities.
Scrum master as a contributor
In the Scrum framework, which claims to be consistent with agile values and principles, the ''scrum master'' role is accountable for ensuring the scrum process is followed and for coaching the scrum team through that process. A common pitfall is for a scrum master to act as a contributor. While not prohibited by the Scrum framework, the scrum master needs to ensure they have the capacity to act in the role of scrum master first and not work on development tasks. A scrum master's role is to facilitate the process rather than create the product.
Having the scrum master also multitasking may result in too many context switches to be productive. Additionally, as a scrum master is responsible for ensuring roadblocks are removed so that the team can make forward progress, the benefit gained by individual tasks moving forward may not outweigh roadblocks that are deferred due to lack of capacity.
Lack of test automation
Due to the iterative nature of agile development, multiple rounds of testing are often needed. Automated testing helps reduce the impact of repeated unit, integration, and regression tests and frees developers and testers to focus on higher value work.
Test automation also supports continued
refactoring
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structure ...
required by iterative software development. Allowing a developer to quickly run tests to confirm refactoring has not modified the functionality of the application may reduce the workload and increase confidence that cleanup efforts have not introduced new defects.
Allowing technical debt to build up
Focusing on delivering new functionality may result in increased
technical debt
In software development, technical debt (also known as design debt or code debt) is the implied cost of additional rework caused by choosing an easy (limited) solution now instead of using a better approach that would take longer.
Analogous with ...
. The team must allow themselves time for defect remediation and refactoring. Technical debt hinders planning abilities by increasing the amount of unscheduled work as production defects distract the team from further progress.
As the system evolves it is important to
refactor
In computer programming and software design, code refactoring is the process of restructuring existing computer code—changing the '' factoring''—without changing its external behavior. Refactoring is intended to improve the design, structure ...
. Over time the lack of constant maintenance causes increasing defects and development costs.
Attempting to take on too much in an iteration
A common misconception is that agile software development allows continuous change, however an iteration backlog is an agreement of what work can be completed during an iteration. Having too much
work-in-progress (WIP) results in inefficiencies such as
context-switching and queueing. The team must avoid feeling pressured into taking on additional work.
Fixed time, resources, scope, and quality
Agile software development fixes time (iteration duration), quality, and ideally resources in advance (though maintaining fixed resources may be difficult if developers are often pulled away from tasks to handle production incidents), while the
scope
Scope or scopes may refer to:
People with the surname
* Jamie Scope (born 1986), English footballer
* John T. Scopes (1900–1970), central figure in the Scopes Trial regarding the teaching of evolution
Arts, media, and entertainment
* Cinem ...
remains variable. The customer or product owner often pushes for a fixed scope for an iteration. However, teams should be reluctant to commit to the locked time, resources and scope (commonly known as the
project management triangle
The project management triangle (called also the ''triple constraint'', ''iron triangle'' and ''project triangle'') is a model of the constraints of project management. While its origins are unclear, it has been used since at least the 1950s. It ...
). Efforts to add scope to the fixed time and resources of agile software development may result in decreased quality.
Developer burnout
Due to the focused pace and continuous nature of agile practices, there is a heightened risk of burnout among members of the delivery team.
Agile management
Agile project management is an iterative development process, where feedback is continuously gathered from users and stakeholders to create the right user experience. Different methods can be used to perform an agile process, these include
scrum
Scrum may refer to:
Sport
* Scrum (rugby), a method of restarting play in rugby union and rugby league
** Scrum (rugby union), scrum in rugby union
* Scrum, an offensive melee formation in Japanese game Bo-taoshi
Media and popular culture
* M ...
,
extreme programming
Extreme programming (XP) is a software development methodology intended to improve software quality and responsiveness to changing customer requirements. As a type of agile software development,"Human Centred Technology Workshop 2006 ", 2006, PD ...
,
lean
Lean, leaning or LEAN may refer to:
Business practices
* Lean thinking, a business methodology adopted in various fields
** Lean construction, an adaption of lean manufacturing principles to the design and construction process
** Lean governmen ...
and
kanban
Kanban (Japanese: カンバン and Chinese: 看板, meaning signboard or billboard) is a scheduling system for lean manufacturing (also called just-in-time manufacturing, abbreviated JIT). Taiichi Ohno, an industrial engineer at Toyota, develope ...
.
The term ''agile management'' is applied to an iterative, incremental method of managing the design and build activities of engineering, information technology and other business areas that aim to provide new product or service development in a highly flexible and interactive manner, based on the principles expressed in the ''Manifesto for Agile Software Development''.
Agile project management metrics help reduce confusion, identify weak points, and measure team's performance throughout the development cycle. Supply chain agility is the ability of a supply chain to cope with uncertainty and variability on offer and demand. An agile supply chain can increase and reduce its capacity rapidly, so it can adapt to a fast-changing customer demand. Finally, strategic agility is the ability of an organisation to change its course of action as its environment is evolving. The key for strategic agility is to recognize external changes early enough and to allocate resources to adapt to these changing environments.
Agile X techniques may also be called
extreme project management
Extreme project management (XPM) refers to a method of managing very complex and very uncertain projects.
Extreme project management differs from traditional project management mainly in its open, elastic and nondeterministic approach. The main ...
. It is a variant of
iterative life cycle where
deliverable
A deliverable is a tangible or intangible good or service produced as a result of a project that is intended to be delivered to a customer (either internal or external). A deliverable could be a report, a document, a software product, a server upgr ...
s are submitted in stages. The main difference between agile and iterative development is that agile methods complete small portions of the deliverables in each delivery cycle (iteration), while iterative methods evolve the entire set of deliverables over time, completing them near the end of the project. Both iterative and agile methods were developed as a reaction to various obstacles that developed in more sequential forms of project organization. For example, as technology projects grow in complexity, end users tend to have difficulty defining the long-term requirements without being able to view progressive prototypes. Projects that develop in iterations can constantly gather feedback to help refine those requirements.
Agile management also offers a simple framework promoting communication and reflection on past work amongst
team
A team is a group of individuals (human or non-human) working together to achieve their goal.
As defined by Professor Leigh Thompson (academic), Leigh Thompson of the Kellogg School of Management, " team is a group of people who are interde ...
members. Teams who were using traditional waterfall planning and adopted the agile way of development typically go through a transformation phase and often take help from agile coaches who help guide the teams through a smoother transformation. There are typically two styles of agile coaching: push-based and
pull-based agile coaching. Here a "push-system" can refer to an upfront estimation of what tasks can be fitted into a sprint (pushing work) e.g. typical with scrum; whereas a "pull system" can refer to an environment where tasks are only performed when work is available e.g. typical for kanban. Agile management approaches have also been employed and adapted to the business and government sectors. For example, within the
federal government of the United States
The federal government of the United States (U.S. federal government or U.S. government) is the national government of the United States, a federal republic located primarily in North America, composed of 50 states, a city within a fede ...
, the
United States Agency for International Development
The United States Agency for International Development (USAID) is an independent agency of the U.S. federal government that is primarily responsible for administering civilian foreign aid and development assistance. With a budget of over $27 bi ...
(USAID) is employing a collaborative project management approach that focuses on incorporating
collaborating, learning and adapting
Adaptive management, also known as adaptive resource management or adaptive environmental assessment and management, is a structured, iterative process of robust decision making in the face of uncertainty, with an aim to reducing uncertainty ove ...
(CLA) strategies to iterate and adapt programming.
Agile methods are mentioned in the ''Guide to the Project Management Body of Knowledge'' (''PMBOK Guide 6th Edition'') under the Product Development Lifecycle definition:
Applications outside software development
![Agile Brazil 2014 conference entrance](https://upload.wikimedia.org/wikipedia/commons/b/b9/Agile_Brazil_2014_conference_entrance.jpg)
According to Jean-Loup Richet (research fellow at
ESSEC
The École Supérieure des Sciences Economiques et Commerciales (more commonly ESSEC Business School or ESSEC) is a major French business and management school, with non-profit association status (French association law of 1901) founded in 1907 ...
Institute for Strategic Innovation & Services) "this approach can be leveraged effectively for non-software products and for project management in general, especially in areas of innovation and uncertainty." The result is a product or project that best meets current customer needs and is delivered with minimal costs, waste, and time, enabling companies to achieve bottom line gains earlier than via traditional approaches.
Agile software development methods have been extensively used for development of software products and some of them use certain characteristics of software, such as
object technologies.
However, these techniques can be applied to the development of non-software products, such as computers, medical devices, food, clothing, and music. Agile software development methods have been used in non-development
IT infrastructure
Information technology infrastructure is defined broadly as a set of information technology (IT) components that are the foundation of an IT service; typically physical components (computer and networking hardware and facilities), but also variou ...
deployments and migrations. Some of the wider principles of agile software development have also found application in general management (e.g., strategy, governance, risk, finance) under the terms
business agility Business agility refers to rapid, continuous, and systematic evolutionary adaptation and entrepreneurial innovation directed at gaining and maintaining competitive advantage. Business agility can be sustained by maintaining and adapting the goods an ...
or agile business management.
Agile software development paradigms can be used in other areas of life such as raising children. Its success in child development might be founded on some basic management principles; communication, adaptation, and awareness. In a
TED Talk
TED Conferences, LLC (Technology, Entertainment, Design) is an American-Canadian non-profit media organization that posts international talks online for free distribution under the slogan "ideas worth spreading". TED was founded by Richard Sau ...
, Bruce Feiler shared how he applied basic agile paradigms to household management and raising children.
Criticism
Agile practices have been cited as potentially inefficient in large organizations and certain types of development. Many organizations believe that agile software development methodologies are too extreme and adopt a hybrid approach that mixes elements of agile software development and plan-driven approaches. Some methods, such as
dynamic systems development method
Dynamic systems development method (DSDM) is an agile project delivery framework, initially used as a software development method. First released in 1994, DSDM originally sought to provide some discipline to the rapid application development (R ...
(DSDM) attempt this in a disciplined way, without sacrificing fundamental principles.
The increasing adoption of agile practices has also been criticized as being a
management fad
Management fad is a term used to characterize a change in philosophy or operations implemented by a business or institution.
The term is subjective and tends to be used in a pejorative sense, as it implies that such a change is being implemented ...
that simply describes existing good practices under new jargon, promotes a ''one size fits all'' mindset towards development strategies, and wrongly emphasizes method over results.
Alistair Cockburn
Alistair Cockburn ( ) is an American computer scientist, known as one of the initiators of the agile movement in software development. He cosigned (with 17 others) the Manifesto for Agile Software Development.
Life and career
Cockburn starte ...
organized a celebration of the 10th anniversary of the ''Manifesto for Agile Software Development'' in Snowbird, Utah on 12 February 2011, gathering some 30+ people who had been involved at the original meeting and since. A list of about 20
elephants in the room ('undiscussable' agile topics/issues) were collected, including aspects: the alliances, failures and limitations of agile software development practices and context (possible causes: commercial interests, decontextualization, no obvious way to make progress based on failure, limited objective evidence, cognitive biases and reasoning fallacies), politics and culture.
As
Philippe Kruchten
Philippe Kruchten (born 1952) is a Canadian software engineer, and Professor of Software Engineering at University of British Columbia in Vancouver, Canada, known as Director of Process Development (RUP) at Rational Software, and developer of the ...
wrote:
The "Manifesto" may have had a negative impact on higher education management and leadership, where it suggested to administrators that slower traditional and deliberative processes should be replaced with more "nimble" ones. The concept rarely found acceptance among university faculty.
Another criticism is that in many ways, agile management and traditional management practices end up being in opposition to one another. A common criticism of this practice is that the time spent attempting to learn and implement the practice is too costly, despite potential benefits. A transition from traditional management to agile management requires total submission to agile and a firm commitment from all members of the organization to seeing the process through. Issues like unequal results across the organization, too much change for employees' ability to handle, or a lack of guarantees at the end of the transformation are just a few examples.
See also
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Cross-functional team
A cross-functional team, also known as a multidisciplinary team or interdisciplinary team, is a group of people with different functional expertise working toward a common goal. It may include people from finance, marketing, operations, and human ...
*
Scrum (software development)
Scrum is a framework for project management with an initial emphasis on software development, although it has been used in other fields including research, sales, marketing and advanced technologies. It is designed for teams of ten or fewer me ...
*
Kanban
Kanban (Japanese: カンバン and Chinese: 看板, meaning signboard or billboard) is a scheduling system for lean manufacturing (also called just-in-time manufacturing, abbreviated JIT). Taiichi Ohno, an industrial engineer at Toyota, develope ...
*
Agile leadership
References
Further reading
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* In
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External links
Agile ManifestoAgile Glossaryof the Agile Alliance
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Martin Fowler's description of the background to agile methods
AgilePatterns.org
{{DEFAULTSORT:Agile Software Development
Software project management
Software development
Software engineering
Software development philosophies