Agile software development Totally Explained

Everything about Agile Software Development totally explained

Agile Software Development is a conceptual framework for software development that promotes development iterations throughout the life-cycle of the project.
   There are many agile development methods; most minimize risk by developing software in short amounts of time. Software developed during one unit of time is referred to as an iteration, which typically lasts from one to four weeks. Each iteration passes through a full software development cycle: including planning, requirements analysis, design, coding, testing, and documentation. An iteration may not add enough functionality to warrant releasing the product to market but the goal is to have an available release (without bugs) at the end of each iteration. At the end of each iteration, the team re-evaluates project priorities.
   Agile methods emphasize face-to-face communication over written documents. Most agile teams are located in a single open office sometimes referred to as a scrum. At a minimum, this includes programmers and their "customers" (customers define the product; they may be product managers, a business analyst, or the clients). The office may include software testers, interaction designers, technical writers, and managers.
   Agile methods also emphasize working software as the primary measure of progress. Combined with the preference for face-to-face communication, agile methods produce very little written documentation relative to other methods. This has resulted in criticism of agile methods as being undisciplined.

History

The modern definition of agile software development evolved in the mid-1990s as part of a reaction against "heavyweight" methods, as typified by a heavily regulated, regimented, micro-managed use of the waterfall model of development. The processes originating from this use of the waterfall model were seen as bureaucratic, slow, demeaning, and inconsistent with the ways that software developers actually perform effective work. A case can be made that agile and iterative development methods are a return to development practice seen early in the history of software development. Initially, agile methods were called "lightweight methods." In 2001, prominent members of the community met at Snowbird, Utah, and adopted the name "agile methods." Later, some of these people formed The Agile Alliance, a non-profit organization that promotes agile development.
A number of methods similar to Agile were created prior to 2000. An adaptive software development process was introduced in a paper by Edmonds (1974). Notable earlier methods include Scrum (1986), Crystal Clear, Extreme Programming (1996), Adaptive Software Development, Feature Driven Development, and Dynamic Systems Development Method(DSDM) (1995). Kent Beck created Extreme Programming (usually abbreviated as "XP") in 1996 as a way to rescue the struggling Chrysler Comprehensive Compensation (C3) project. While Chrysler eventually canceled that project, the method was refined by Ron Jeffries' full-time XP coaching, public discussion on Ward Cunningham's Portland Pattern Repository wiki and further work by Beck, including a book in 1999. in the field of agile development (then called "light-weight methods") came together at the Snowbird ski resort in Utah to discuss ways of creating software in a lighter, faster, more people-centric way. They created the Agile Manifesto, widely regarded as the canonical definition of agile development and accompanying agile principles.
Some of the principles behind the Agile Manifesto are:

Customer satisfaction by rapid, continuous delivery of useful software
Working software is delivered frequently (weeks rather than months)
Working software is the principal measure of progress
Even late changes in requirements are welcomed
Close, daily cooperation between business people and developers
Face-to-face conversation is the best form of communication (Co-location)
Projects are built around motivated individuals, who should be trusted
Continuous attention to technical excellence and good design
Simplicity
Self-organizing teams
Regular adaptation to changing circumstances

The manifesto spawned a movement in the software industry known as agile software development.
In 2005, Alistair Cockburn and Jim Highsmith gathered another group of people — management experts, this time — and wrote an addendum, known as the PM Declaration of Interdependence.

Comparison with other methods

Agile methods are sometimes characterized as being at the opposite end of the spectrum from "plan-driven" or "disciplined" methods. This distinction is misleading, as it implies that agile methods are "unplanned" or "undisciplined". A more accurate distinction is that methods exist on a continuum from "adaptive" to "predictive". Agile methods lie on the "adaptive" side of this continuum.
   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 can report exactly what tasks are being done next week, but only which features are planned for next month. When asked about a release six months from now, an adaptive team may only be able to report the mission statement for the release, or a statement of expected value vs. cost.
   Predictive methods, in contrast, focus on planning the future in detail. A predictive team can report exactly what features and tasks are planned for the entire length of the development process. Predictive teams have difficulty changing direction. The plan is typically optimized for the original destination and changing direction can cause completed work to be thrown away and done over differently. 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.

Contrasted with other iterative development methods

Most agile methods share other iterative and incremental development methods' emphasis on building releasable software in short time periods. Agile development differs from other development models: in this model time periods are measured in weeks rather than months and work is performed in a highly collaborative manner. Most agile methods also differ by treating their time period as a strict timebox.

Contrasted with the waterfall model

Agile development has little in common with the waterfall model. As of 2008, the waterfall model is still in common use. The waterfall model is the most predictive of the methods, stepping through requirements capture, analysis, design, coding, and testing in a strict, pre-planned sequence. Progress is generally measured in terms of deliverable artifacts: requirement specifications, design documents, test plans, code reviews and the like.
   The main problem with the waterfall model is the inflexible division of a project into separate stages, so that commitments are made early on, and it's difficult to react to changes in requirements. Iterations are expensive. This means that the waterfall model is likely to be unsuitable if requirements are not well understood or are likely to change in the course of the project. Agile methods, in contrast, produce completely developed and tested features (but a very small subset of the whole) every few weeks or months. The emphasis is on obtaining the smallest workable piece of functionality to deliver business value early, and continually improving it/adding further functionality throughout the life of the project.
   In this respect, agile critics incorrectly assert that these features are not placed in context of the overall project, concluding that, if the sponsors of the project are concerned about completing certain goals with a defined timeline or budget, agile may not be appropriate. Adaptations of Scrum show how agile methods are augmented to produce and continuously improve a strategic plan.
   Some agile teams use the waterfall model on a small scale, repeating the entire waterfall cycle in every iteration. Other teams, most notably Extreme Programming teams, work on activities simultaneously.

Contrasted with "cowboy coding"

Cowboy coding is the absence of a defined method: team members do whatever they feel is right. Agile development's frequent re-evaluation of plans, emphasis on face-to-face communication, and relatively sparse use of documents sometimes causes people to confuse it with cowboy coding. Agile teams, however, do follow defined (and often very disciplined and rigorous) processes.
As with all development methods, the skill and experience of the users determine the degree of success and/or abuse of such activity. The more rigid controls systematically embedded within a process offer stronger levels of accountability of the users. The degradation of well-intended procedures can lead to activities often categorized as cowboy coding.

Suitability of agile methods

There is little if any consensus on what types of software projects are best suited for agile methodologies. Many large organizations have difficulty bridging the gap between a more traditional waterfall methodology and an agile one.
   Large scale agile software development remains an active research area.
   Agile development has been widely documented (see Experience Reports, below, as well as Beck pg. 157, and Boehm and Turner pg. 55-57) as working well for small (<10 developers) co-located teams.
   Some things that can negatively impact the success of an agile project are:

Large scale development efforts (>20 developers), though scaling strategies and evidence to the contrary have been described.

Distributed development efforts (non-co-located teams). Strategies have been described in Bridging the Distanceand Using an Agile Software Process with Offshore Development

Command-and-control company cultures

Forcing an agile process on a development team Several successful large scale agile projects have been documented. BT has had several hundred developers situated in the UK, Ireland and India working collaboratively on projects and using Agile methods. While questions undoubtedly still arise about the suitability of some Agile methods to certain project types, it would appear that scale or geography, by themselves, are not necessarily barriers to success. Barry Boehm and Richard Turner suggest that risk analysis be used to choose between adaptive ("agile") and predictive ("plan-driven") methods. 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. 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).
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. There are no experience reports in which all the XP practices have been adopted. Instead, a partial adoption of XP practices, as suggested by Beck, has been reported on several occasions.
A distinction can be made between static method adaptation and dynamic method adaptation. The key assumption behind static method adaptation is that the project context is given at the start of a project and remains fixed during project execution. The result is a static definition of the project context. Given such a definition, route maps can be used in order to determine which structured method fragments should be used for that particular project, based on predefined sets of criteria. Dynamic method adaptation, in contrast, assumes that projects are situated in an emergent context. An emergent context implies that a project has to deal with emergent factors that affect relevant conditions but are not predictable. This also means that a project context isn't fixed, but changing during project execution. In such a case prescriptive route maps are not appropriate. The practical implication of dynamic method adaptation is that project managers often have to modify structured fragments or even innovate new fragments, during the execution of a project (Aydin et al, 2005).

Agile methods and project management

Agile methods differ to a large degree in the way they cover project management. Some methods are supplemented with guidelines on project management, but there's generally no comprehensive support. PRINCE2 has been suggested as a suitable, complementary project management system.

Project management tools for agile development teams

A number of project management tools are specifically aimed at agile development. They are designed to help plan, track, analyse and integrate work. These tools play an important role in agile development, as a means of Knowledge Management.
Common features include: Version control integration, progress tracking, easy work allocation, integrated release and iteration planning, discussion forums, and reporting and tracking of software defects
Some well-known agile project management websites include: versionone, targetprocess, assembla, rallydev, ppts, Gatherspace and visionproject.

Agile methods

Some of the well-known agile software development methods:

Agile Modeling

Agile Unified Process (AUP)

Agile Data Method

Daily kickoff and review of goals

short release cycles

Responsive Development

Generalism - Use of generic skill sets that are common across the team, not reliance on specific skill sets that are scarce

Test Driven Development (TDD)

Feature Driven Development (FDD)

Behavior Driven Development (BDD)

Essential Unified Process (EssUP) Other approaches:

Software Development Rhythms

Agile Documentation

ICONIX Process

Microsoft Solutions Framework (MSF)

Database refactoring

Agile beyond software development

Agile software development depends on some special characteristics possessed only by software, such as object technologies and the ability to automate testing. However, related techniques have been created for developing non-software products, such as semiconductors, motor vehicles, or chemicals. For more on them, see Flexible product development.

Measuring agility

While many see agility as a means to an end, a number of approaches have been proposed to quantify agility. Agility Index Measurements (AIM)(External Link

) score projects against a number of agility factors to achieve a total. The similarly-named Agility Measurement Index (External Link

), scores developments against five dimensions of a software project (duration, risk, novelty, effort, and interaction). Other techniques are based on measurable goals (External Link

). Another study using fuzzy mathematics has suggested that project velocity can be used as a metric of agility.
While such approaches have been proposed to measure agility, the practical application of such metrics has yet to be seen.

Criticism

Agile development is sometimes criticized as cowboy coding. Extreme Programming's initial buzz and controversial tenets, such as pair programming and continuous design, have attracted particular criticism, such as McBreen and Boehm and Turner.
In particular, Extreme Programming is reviewed and critiqued by Matt Stephens's and Doug Rosenberg's Extreme Programming Refactored. Criticisms include:

Lack of structure and necessary documentation

Only works with senior-level developers

Incorporates insufficient software design

Requires too much cultural change to adopt

Can lead to more difficult contractual negotiations

Can be very inefficient — if the requirements for one area of code change through various iterations, the same programming may need to be done several times over. Whereas if a plan were there to be followed, a single area of code is expected to be written once.

Impossible to develop realistic estimates of work effort needed to provide a quote, because at the beginning of the project no one knows the entire scope/requirements

Drastically increases the risk of scope creep due to the lack of detailed requirements documentation

Agile is feature driven, non-functional quality attributes are hard to be placed as user stories The criticisms regarding insufficient software design and lack of documentation are addressed by the Agile Modeling method, which can easily be tailored into agile processes such as XP.
Agile software development has been criticized because it may not bring about all of the claimed benefits when programmers of average ability use this method.

Post-Agilism

In software engineering, post-Agilism (aka "Fragilism") is an informal movement of practitioners who have chosen to draw from a much wider range of methods and schools of thought on software development, preferring to avoid being constrained by what they consider to be "Agile Dogma" (or "Agile with a capital 'A'")
   It is argued that the meaning of Agile is ambiguous and being inappropriately applied to a very wide range of approaches like Six Sigma and CMMi. It is also argued that "Agile", "evolutionary", and "lean" (as in Lean software development) don't mean the same thing in practice, even though they're all lumped under the banner of "Agile" - possibly for marketing purposes.
   Proponents also argue that process-oriented methods, especially methods that rely on repeatable results and that incrementally reduce waste and process variation like Six Sigma, have a tendency to limit an organisation's adaptive capacity (their "slack"), making them less able to respond to discontinuous change - for example, less agile. It is proposed that "agile", "lean" and "evolutionary" are strategies that need to be properly understood and appropriately applied to any specific context. That is, there's a time to be "agile", a time to be "lean" and a time to be "evolutionary".
   Much of post-Agile thinking centers around Nonlinear Management, a superset of management techniques that include many Agile practices.
   Some commentators propose a model of post-Agilism that's effectively constructive anarchy, in that teams should be self-organising to the point where even the core values of the Agile movement are considered too presciptive, and that teams should simply "do whatever works for them".

Experience reports

Agile development has been the subject of several conferences. Some of these conferences have had academic backing and included peer-reviewed papers, including a peer-reviewed experience report track. The experience reports share industry experiences with agile software development.
As of 2006, experience reports have been or will be presented at the following conferences:

XP (2000, 2001, 2002, 2003, 2004, 2005, 2006)

XP Universe (2001)

XP/Agile Universe (2002,2003, 2004)

Agile Development Conference (2003, 2004,) (peer-reviewed; proceedings published by IEEE?)

Agile (2005, 2006) (peer-reviewed; proceedings published by IEEE)Further Information

Get more info on 'Agile Software Development'.

External Link Exchanges

Do you know how hard it is to get a link from a large encyclopaedia? Well we're different and will prove it. To get a link from us just add the following HTML to your site on a relevant page:

<a href="http://agile_software_development.totallyexplained.com">Agile software development Totally Explained</a>

Then simply click through this link from your web page. Our crawlers will verify your link, extract the title of your web page and instantly add a link back to it. If you like you can remove the words Totally Explained and embed the link in article text.
As long as your link remains in place, we'll keep our link to you right here. Please play fair - our crawlers are watching. Your site must be closely related to this one's topic. Any kind of spamming, dubious practises or removing the link will result in your link from us being dropped and, potentially, your whole site being banned.