Agile Web Development


Agile software development is a group of software development methods based on iterative and incremental development, where requirements and solutions evolve through collaboration between self-organizing, cross-functional teams. It promotes adaptive planning, evolutionary development and delivery, a time-boxed iterative approach, and encourages rapid and flexible response to change. It is a conceptual framework that promotes foreseen interactions throughout the development cycle. The Agile Manifesto[1] introduced the term in 2001.

Software development process
software developer at work
Activities and steps and for controlling
Methodologies
Supporting disciplines
Tools

History

Predecessors

Incremental software development methods have been traced back to 1957.[2] In 1974, a paper by E. A. Edmonds introduced an adaptive software development process.[3] Concurrently and independently the same methods were developed and deployed by the New York Telephone Company's Systems Development Center under the direction of Dan Gielan. In the early 1970s, Tom Gilb started publishing the concepts of Evolutionary Project Management (EVO), which has evolved into Competitive Engineering.[4] During the mid to late 1970s Gielan lectured extensively throughout the U.S. on this methodology, its practices, and its benefits.

So-called lightweight agile software development methods evolved in the mid-1990s as a reaction against the heavyweight waterfall-oriented methods, which were characterized by their critics as being heavily regulated, regimented, micromanaged and overly incremental approaches to development.

Proponents of lightweight agile methods contend that they are a return to development practices that were present early in the history of software development.[2]

Early implementations of agile methods include Rational Unified Process (1994), Scrum (1995), Crystal Clear, Extreme Programming (1996), Adaptive Software Development, Feature Driven Development (1997), and Dynamic Systems Development Method (DSDM) (1995). These are now collectively referred to as agile methodologies, after the Agile Manifesto was published in 2001.[5]

Agile Manifesto

In February 2001, 17 software developers[6] met at the Snowbird, Utah, resort, to discuss lightweight development methods. They published the Manifesto for Agile Software Development[1] to define the approach now known as agile software development. Some of the manifesto's authors formed the Agile Alliance, a nonprofit organization that promotes software development according to the manifesto's principles.

The Agile Manifesto reads, in its entirety, as follows:

We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value:
Individuals and interactions over processes and tools
Working software over comprehensive documentation
Customer collaboration over contract negotiation
Responding to change over following a plan
That is, while there is value in the items on the right, we value the items on the left more.[1]

The meanings of the manifesto items on the left within the agile software development context are described below:

  • Individuals and interactions – in agile development, self-organization and motivation are important, as are interactions like co-location and pair programming.
  • Working software – working software will be more useful and welcome than just presenting documents to clients in meetings.
  • Customer collaboration – requirements cannot be fully collected at the beginning of the software development cycle, therefore continuous customer or stakeholder involvement is very important.
  • Responding to change – agile development is focused on quick responses to change and continuous development.[7]

The Agile Manifesto is based on twelve principles:[8]

  1. Customer satisfaction by rapid delivery of useful software
  2. Welcome changing requirements, even late in development
  3. Working software is delivered frequently (weeks rather than months)
  4. Working software is the principal measure of progress
  5. Sustainable development, able to maintain a constant pace
  6. Close, daily cooperation between business people and developers
  7. Face-to-face conversation is the best form of communication (co-location)
  8. Projects are built around motivated individuals, who should be trusted
  9. Continuous attention to technical excellence and good design
  10. Simplicity—the art of maximizing the amount of work not done—is essential
  11. Self-organizing teams
  12. Regular adaptation to changing circumstances

The well-known background picture of the Agile Manifesto website was taken by Ward Cunningham, who wanted to capture the moment during the weekend meeting at Snowbird.[9]

In 2005, a group headed by Alistair Cockburn and Jim Highsmith wrote an addendum of project management principles, the Declaration of Interdependence,[10] to guide software project management according to agile development methods.

In 2009, a movement spearheaded by Robert C Martin wrote an extension of software development principles, the Software Craftsmanship Manifesto, to guide agile software development according to professional conduct and mastery.

Characteristics

There are many specific agile development methods. Most promote development, teamwork, collaboration, and process adaptability throughout the life-cycle of the project.

Agile methods break tasks into small increments with minimal planning and do not directly involve long-term planning. Iterations are short time frames (timeboxes) that typically last from one to four weeks. Each iteration involves a cross functional team working in all functions: planning, requirements analysis, design, coding, unit testing, and acceptance testing. At the end of the iteration a working product is demonstrated to stakeholders. This minimizes overall risk and allows the project 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.[11] Multiple iterations might be required to release a product or new features.

No matter what development disciplines are required, each agile team will contain a customer representative. This person is appointed by stakeholders to act on their behalf[12] and makes a personal commitment to being available for developers to answer mid-iteration questions. At the end of each iteration, stakeholders and the customer representative review progress and re-evaluate priorities with a view to optimizing the return on investment (ROI) and ensuring alignment with customer needs and company goals.

A common characteristic of agile development are daily status meetings or "stand-ups". In a brief session, team members report to each other what they did the previous day, what they intend to do today, and what their roadblocks are.

Specific tools and techniques, such as continuous integration, automated or xUnit test, pair programming, test-driven development, design patterns, domain-driven design, code refactoring and other techniques are often used to improve quality and enhance project agility.

Light Agile Development (LAD) is a flavor of agile methodology that applies hand picked techniques from the wider range of agile practices to suit different companies, development teams, situations and environments. Another key aspect of LAD is that it tends to be user-centric, focusing primarily on the user experience and usable software interfaces and uses agile methodologies to deliver them. Most real-world implementations of Agile are really LAD in practice, since a core value of the method is flexibility, sensibility, and focus on getting stuff done.

In agile software development, an information radiator is a (normally large) physical display located prominently in an office, where passers-by can see it. It presents an up-to-date summary of the status of a software project or other product.[13][14] The name was coined by Alistair Cockburn, and described in his 2002 book Agile Software Development.[14] A build light indicator may be used to inform a team about the current status of their project.

Comparison with other methods

Methods exist on a continuum from adaptive to predictive.[15] Agile 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.[16] 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 will have difficulty describing exactly what will happen in the future. The further away a date is, the more vague an adaptive method will be 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 will often institute a change control board to ensure that only the most valuable changes are considered.

Agile methods have much in common with the Rapid Application Development techniques from the 1980/90s as espoused by James Martin and others. In addition to technology-focused methods, customer- and design-centered methods, such as Visualization-Driven Rapid Prototyping developed by Brian Willison, work to engage customers and end users to facilitate agile software development.

In 2008 the Software Engineering Institute (SEI) published the technical report "CMMI or Agile: Why Not Embrace Both"[17] to make clear that Capability Maturity Model Integration and agile can co-exist. CMMI Version 1.3 includes tips for implementing Agile and CMMI.[18]One of the differences between agile and waterfall is that testing of the software is conducted at different points during the software development lifecycle. In the waterfall model, there is a separate testing phase near the point of implementation. In Agile XP, testing is done concurrently with implementation.

Agile methods

Well-known agile software development methods 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:

A process or capability in which human agents determine a system development approach for a specific project situation through responsive changes in, and dynamic interplays between contexts, intentions, and method fragments.[21]

Potentially, almost all agile methods are suitable for method tailoring. Even the DSDM method is being used for this purpose and has been successfully tailored in a CMM context.[22] Situation-appropriateness can be considered as a distinguishing characteristic between agile methods and traditional software development methods, with the latter being relatively much more rigid and prescriptive. The practical implication is that agile methods allow project teams to adapt working practices according to the needs of individual projects. Practices are concrete activities and products that are part of a method framework. At a more extreme level, the philosophy behind the method, consisting of a number of principles, could be adapted (Aydin, 2004).[21]

Extreme Programming (XP) makes the need for method adaptation explicit. One of the fundamental ideas of XP is that no one process fits every project, but rather that practices should be tailored to the needs of individual projects. Partial adoption of XP practices, as suggested by

Software development life cycle

The agile methods are focused on different aspects of the software development life cycle. Some focus on the practices (extreme programming, pragmatic programming, agile modeling), while others focus on managing the software projects (the scrum approach). Yet, there are approaches providing full coverage over the development life cycle (dynamic systems development method, or DSDM, and the IBM Rational Unified Process, or RUP), while most of them are suitable from the requirements specification phase on (feature-driven development, or FDD, for example). Thus, there is a clear difference between the various agile software development methods in this regard. Whereas DSDM and RUP do not need complementing approaches to support software development, the others do to a varying degree. DSDM can be used by anyone (although only DSDM members can offer DSDM products or services). RUP, then, is a commercially sold development environment (Abrahamsson, Salo, Rankainen, & Warsta, 2002).[23]

Measuring agility

While agility can be seen as a means to an end, a number of approaches have been proposed to quantify agility. Agility Index Measurements (AIM)[25] score projects against a number of agility factors to achieve a total. The similarly named Agility Measurement Index,[26] scores developments against five dimensions of a software project (duration, risk, novelty, effort, and interaction). Other techniques are based on measurable goals.[27] Another study using fuzzy mathematics[28] has suggested that project velocity can be used as a metric of agility. There are agile self-assessments to determine whether a team is using agile practices (Nokia test,[29] Karlskrona test,[30] 42 points test[31]).

While such approaches have been proposed to measure agility, the practical application of such metrics is still debated. There is agile software development ROI data available from the CSIAC ROI Dashboard.[32]

Experience and reception

One of the early studies reporting gains in quality, productivity, and business satisfaction by using Agile methods was a survey conducted by Shine Technologies from November 2002 to January 2003.[33] A similar survey conducted in 2006 by Scott Ambler, the Practice Leader for Agile Development with IBM Rational's Methods Group reported similar benefits.[34] Others claim that agile development methods are still too young to require extensive academic proof of their success.[35]

Suitability

Large-scale agile software development remains an active research area.[36][37]

Agile development has been widely seen as being more suitable for certain types of environment, including small teams of experts.[38][39]:157

Positive reception towards Agile methods has been observed in Embedded domain across Europe in recent years.[40]

Some things that may negatively impact the success of an agile project are:

  • Large-scale development efforts (>20 developers), though scaling strategies[37] and evidence of some large projects[41] have been described.
  • Distributed development efforts (non-colocated teams). Strategies have been described in Bridging the Distance[42] and Using an Agile Software Process with Offshore Development.[43]
  • Forcing an agile process on a development team.[44]
  • Mission-critical systems where failure is not an option at any cost (e.g. software for air traffic control).

The early successes, challenges and limitations encountered in the adoption of agile methods in a large organization have been documented.[45]

In terms of outsourcing agile development, Michael Hackett, Sr. Vice President of LogiGear Corporation has stated that "the offshore team ... should have expertise, experience, good communication skills, inter-cultural understanding, trust and understanding between members and groups and with each other."[46]

Agile methods have been extensively used for development of software products and some of them use certain characteristics of software, such as object technologies.[47] However, these techniques can be applied to the development of non-software products, such as computers, motor vehicles, medical devices, food, and clothing; see Flexible product development.

Risk analysis can also be used to choose between adaptive (agile or value-driven) and predictive (plan-driven) methods.[48] Barry Boehm and Richard Turner suggest that each side of the continuum has its own home ground, as follows:[38]

Suitability of different development methods
Agile home ground Plan-driven home ground Formal methods
Low criticality High criticality Extreme criticality
Senior developers Junior developers Senior developers
Requirements change often Requirements do not change often Limited requirements, limited features see Wirth's law
Small number of developers Large number of developers Requirements that can be modeled
Culture that responds to change Culture that demands order Extreme quality

Criticism

Agile methodologies can also be inefficient in large organizations and certain types of projects (see paragraph "Suitability"). Agile methods seem best for developmental and non-sequential projects. Many organizations believe that agile methodologies are too extreme and adopt a hybrid approach that mixes elements of agile and plan-driven approaches.[49]

The term "agile" has also been criticized as being a management fad 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.[50]

Alistair Cockburn organized a celebration of the 10th anniversary of the Agile Manifesto in Snowbird, Utah on February 12, 2011, gathering some 30+ people who’d 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 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.[51]

See also

References

Further reading

  • Abrahamsson, P., Salo, O., Ronkainen, J., & Warsta, J. (2002). Agile Software Development Methods: Review and Analysis. VTT Publications 478.
  • Cohen, D., Lindvall, M., & Costa, P. (2004). An introduction to agile methods. In Advances in Computers (pp. 1–66). New York: Elsevier Science.
  • Dingsøyr, Torgeir, Dybå, Tore and Moe, Nils Brede (ed.): , Springer, Berlin Heidelberg, 2010.
  • Fowler, Martin. . Appeared in Extreme Programming Explained, G. Succi and M. Marchesi, ed., Addison-Wesley, Boston. 2001.
  • Larman, Craig and Basili, Victor R. IEEE Computer, June 2003
  • Riehle, Dirk. . Appeared in Extreme Programming Explained, G. Succi and M. Marchesi, ed., Addison-Wesley, Boston. 2001.
  • M. Stephens, D. Rosenberg. Extreme Programming Refactored: The Case Against XP. Apress L.P., Berkeley, California. 2003. (ISBN 1-59059-096-1)
  • Shore, J., & Warden S. (2008). The Art of Agile Development. O'Reilly Media, Inc.
  • Willison, Brian (2008). Iterative Milestone Engineering Model. New York, NY.
  • Willison, Brian (2008). Visualization Driven Rapid Prototyping. Parsons Institute for Information Mapping.
  • Wollmuth, Christine. "Risky Business". 2013

External links

  • DMOZ
  • R/GA), October 22, 2001
  • Martin Fowler's description of the background to agile methods
  • Ten Authors of The Agile Manifesto Celebrate its Tenth Anniversary
  • A look into the PMI-ACP (Agile Certified Practitioner)
  • Agile Manifesto
  • Agile Alliance
  • Scrum.org
  • Scrum Alliance

This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and USA.gov, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for USA.gov and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
 
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
 
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.