Agile software development 639009 225940136 2008-07-16T03:06:57Z Iterator12n 4538558 [[WP:UNDO|Undid]] revision 225939560 by [[Special:Contributions/72.83.125.105|72.83.125.105]] ([[User talk:72.83.125.105|talk]]) rm text that lacks a source and is questionable {{expert|date=April 2007}} {{nofootnotes|date=June 2008}} {{Software development process}} The term '''Agile Software Development''' refers to a group of [[software development]] methodologies that promotes development [[iterations#Project management|iterations]], open collaboration, and process adaptability throughout the life-cycle of the project. == Introduction == There are many agile development methods; most minimize risk by developing software in multiple repetitions (or 'iterations') of short time frames (known as 'timeboxes'). Software developed during one unit of time is referred to as an iteration, which typically lasts from two to four weeks. Each iteration passes through a full software development cycle, including planning, [[requirements analysis]], design, writing [[Unit_test|unit tests]], then coding until the unit tests pass and a working product is finally demonstrated to stakeholders. Documentation is no different than software design and coding. It, too, is produced as required by stakeholders. An iteration may not add enough functionality to warrant releasing the product to market, but the goal is to have an available release (without [[Software bug|bugs]]) at the end of each iteration. At the end of each iteration, stakeholders re-evaluate project priorities with a view to optimizing their [[return on investment]]. Agile methods emphasize face-to-face communication over written documents. Most agile teams are located in a single open office to facilitate such communication. One agile management methodology, [[Scrum (development)|Scrum]], advocates a team size of 5 to 9. Larger teams than 9 should be split into smaller teams to help make team communication and team collaboration easier. Team composition in an agile project is usually cross-functional and self-organising without consideration for any existing corporate hierarchy or the corporate roles of team members. No matter what development disciplines are required, at a minimum, every agile team will contain a customer representative. This person is appointed by stakeholders to act on their behalf and makes a personal commitment to being available for developers to answer mid-iteration problem-domain questions. This availability is critical to agile project success. Part of the [[Scrum (development)|Scrum]] methodology is routine and formal daily face-to-face communication between team members. This specifically includes the customer representative and any interested stakeholders as observers. Known as a daily scrum, team members report to each other what they did yesterday, what they intend to do today, and what their roadblocks are. This formalised face-to-face communication prevents problems being hidden, provided that someone with corporate influence is always listening. For the Scrum methodology, this is the Scrum Master. Otherwise it is the agile project manager. Agile methods emphasize working software as the primary measure of progress. Combined with the preference for face-to-face communication, agile methods usually produce less written documentation than other methods. In an agile project, documentation, Gantt charts and other project artifacts all rank equally with working product. However, when stakeholders are asked to prioritise deliverables for demonstration at the end of the current iteration, they generally prefer to see working product. Stakeholders are encouraged to prioritise iteration outcomes based exclusively on business value perceived at the beginning of the iteration. If documentation represents higher business value than working software in any particular iteration then stakeholders give it a higher priority than working software. The (cross-functional) development team will accordingly produce that documentation instead of lower priority software.{{Fact|date=June 2008}} Agile means being able to quickly change direction. In software development, it requires strong discipline to code for agility. It includes writing tests for functionality before coding. It calls for [[Domain-driven design|naming]] of functionality to exactly match the intent and the terminology of the problem domain. It demands cessation of coding when the tests pass. The sum total of all the disciplines delivers an ability to change direction quickly. New and unexpected functionality required to cope with a sudden change in the business landscape can be inserted in existing code using [[test-driven development]] and all the previous tests will pass or fail to instantly indicate where code needs to be refactored to stay functional. If functionality is added before it is required then it becomes "dead weight" when refactoring is called for. ==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.<ref>[[Gerald M. Weinberg]]: ''We were doing incremental development as early as 1957, in Los Angeles, under the direction of Bernie Dimsdale [at IBM’s ServiceBureau Corporation]. He was a colleague of John von Neumann, 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, indistinguishable from XP. [. . .] 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. '' quoted in {{cite journal | last = Larman | first = Craig | coauthors = Victor R. Basili | year = 2003 | month = June | title = Iterative and Incremental Development: A Brief History | journal = Computer | volume = 36 | issue = No. 6 | pages = pp 47–56 | doi = 10.1109/MC.2003.1204375 | url = http://www2.umassd.edu/SWPI/xp/articles/r6047.pdf | format = pdf | accessdate = 2007-02-22}} ([http://www.agilealliance.org/show/1404 Permission note])</ref> Initially, agile methods were called "lightweight methods." In 2001, prominent members of the community met at [[Snowbird, Utah|Snowbird]], [[Utah]], and adopted the name "agile methods." Later, some of these people formed The [[Agile Alliance]]<ref>[http://www.agilealliance.com Agile Alliance]</ref>, 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)<ref name="edmonds1974">{{Citation| last=Edmonds| first=E. A.| title= A process for the development of software for non-technical users as an adaptive system| journal=General Systems| volume=XIX| year=1974| pages=215–218}}</ref>. Notable earlier methods include [[Scrum (management)|Scrum]] (1986), [[Crystal Clear (software development)|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.<ref name="beck1999"/> Elements of Extreme Programming appear to be based on [[Scrum (in management)|Scrum]] and [[Ward Cunningham]]'s [[Episodes pattern language]]. ==Principles behind agile methods — The Agile Manifesto== {{seealso|Agile Manifesto}} Agile methods are a family of development processes, not a single approach to software development. In 2001, 17 prominent figures<ref>[[Kent Beck]], [[Mike Beedle]], [[Arie van Bennekum]], [[Alistair Cockburn]], [[Ward Cunningham]], [[Martin Fowler]], [[James Grenning]], [[Jim Highsmith]], [[Andy Hunt (author)|Andrew Hunt]], [[Ron Jeffries]], [[Jon Kern]], [[Brian Marick]], [[Robert C. Martin]], [[Steve Mellor]], [[Ken Schwaber]], [[Jeff Sutherland]] and [[Dave Thomas (programmer)|Dave Thomas]]</ref> 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<ref name="manifestoprinciples">[http://www.agilemanifesto.org/principles.html Agile Manifesto principles]</ref> 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".<ref "boehm2004App">{{cite book|last=Boehm|first=B.|authorlink=Barry Boehm|coauthors=[[Richard Turner (software)|R. Turner]]|title=Balancing Agility and Discipline: A Guide for the Perplexed|publisher=Addison-Wesley|location=Boston, MA|year=2004|id=ISBN 0-321-18612-5}} Appendix A, pages 165-194 </ref> 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.<ref name="Laplante2004">{{cite journal|last=Laplante |first=P.A. |coauthors= C.J. Neill|url=http://www.acmqueue.com/modules.php?name=Content&pa=showpage&pid=110 |title="The Demise of the Waterfall Model Is Imminent" and Other Urban Myths |journal=[[Association for Computing Machinery|ACM]] Queue |volume=1|issue=10|month=February|year=2004|accessdate = 2006-05-13|doi=10.1145/971564.971573|pages=10}}</ref> 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 is 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.<ref>{{cite book | last = Sommerville | first = Ian | authorlink = Ian Sommerville | title = Software engineering| origyear = 1982 | edition = 8th edition | publisher = [[Addison Wesley]] | year = 2007 | location=Harlow | ISBN = 0-321-31379-8 | pages = pp 66f | chapter = 4.1.1. The waterfall model}}</ref> 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 (development)| Scrum]]<ref name="Ambler2008">{{cite journal|last=Ambler|first=S.|url=http://www.drdobbsonline.net/architect/207100381|title="Scaling Scrum - Meeting Real World Development Needs|journal=Dr. Dobbs|month=April|year=2008|accessdate = 2008-04-23}}</ref> 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.<ref>As [http://heavylogic.com/agile.php reported] by [http://heavylogic.com HeavyLogic]</ref> 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 method and an agile one. Large scale agile software development remains an active research area.<ref name="oopsla2002">Agile Processes Workshop II Managing Multiple Concurrent Agile Projects. Washington: OOPSLA 2002</ref><ref name="ambler2006">"Supersize Me" in Dr. Dobb's Journal, [[February 15]] [[2006]].</ref> Agile development has been widely documented (see [[#Experience Reports|Experience Reports]], below, as well as Beck<ref name="beck1999">{{cite book|last=Beck|first=K.|authorlink=Kent Beck|title=Extreme Programming Explained: Embrace Change|publisher=Addison-Wesley|location=Boston, MA|year=1999|id=ISBN 0-321-27865-8}}</ref> pg. 157, and Boehm and Turner<ref name="boehm2004">{{cite book|last=Boehm|first=B.|authorlink=Barry Boehm|coauthors=[[Richard Turner (software)|R. Turner]]|title=Balancing Agility and Discipline: A Guide for the Perplexed|publisher=Addison-Wesley|location=Boston, MA|year=2004|id=ISBN 0-321-18612-5}}</ref> 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<ref name="supersizeme"> [http://www.sdmagazine.com/documents/s=10020/sdm0603g/0603g.html Supersize Me]</ref> and evidence to the contrary<ref name="sstc2007"> Schaaf, R.J. (2007). "Agility XL", [http://www.sstc-online.org/Proceedings/2007/pdfs/RJS1722.pdf Systems and Software Technology Conference 2007], Tampa, FL </ref> have been described. * Distributed development efforts (non-co-located teams). Strategies have been described in ''Bridging the Distance''<ref name="BridgingTheDistance"> [http://www.sdmagazine.com/documents/s=7556/sdm0209i/sdm0209i.htm Bridging the Distance] </ref>and ''Using an Agile Software Process with Offshore Development''<ref name="AgileOffshore">[http://www.martinfowler.com/articles/agileOffshore.html Using an Agile Software Process with Offshore Development]</ref> * Command-and-control company cultures * Forcing an agile process on a development team Several successful large scale agile projects have been documented. [[British Telecom|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 (software)|Richard Turner]] suggest that [[risk analysis]] be used to choose between adaptive ("agile") and predictive ("plan-driven") methods.<ref name="boehm2004"/> The authors suggest that each side of the continuum has its own ''home ground'' as follows: Agile home ground: * Low criticality * Senior developers * Requirements change very often * Small number of developers * Culture that thrives on chaos Plan-driven home ground: * High criticality * Junior developers * Requirements don't change too often * Large number of developers * Culture that demands order ==Agile Data== The [http://www.agiledata.org Agile Data method] describes how data professionals can be productive members of agile software development teams. Agile Data's [http://www.agiledata.org/essays/philosophies.html 6 philosophies] provide guidance for how data professionals can interact effectively with other team members as traditional approaches to data work don't fit well with agile approaches. More importantly the Agile Data method describes a collection of agile techniques that DBAs can adopt, including [[Database refactoring]], agile data modeling, database regression testing, and continuous database integration. ==Agile methods and 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: <blockquote>A process or capability in which human agents through responsive changes in, and dynamic interplays between contexts, intentions, and method fragments determine a system development approach for a specific project situation.<ref name= "Aydin2004"> Aydin, M.N., Harmsen, F., Slooten, K. v., & Stagwee, R. A. (2004). An Agile Information Systems Development Method in use. ''Turk J Elec Engin, 12(2),'' 127-138</ref></blockquote> 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 [[Capability Maturity Model|CMM]] context.<ref name="Abrahamsson2003"> Abrahamsson, P., Warsta, J., Siponen, M.T., & Ronkainen, J. (2003). New Directions on Agile Methods: A Comparative Analysis. ''Proceedings of ICSE'03'', 244-254</ref> 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).<ref name="Aydin2004"> Aydin, M.N., Harmsen, F., Slooten, K. v., & Stagwee, R. A. (2004). An Agile Information Systems Development Method in use. ''Turk J Elec Engin, 12(2),'' 127-138</ref> 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 [[Kent Beck|Beck]], has been reported on several occasions.<ref name="Abrahamsson2002"> Abrahamsson, P., Salo, O., Ronkainen, J., & Warsta, J. (2002). Agile Software Development Methods: Review and Analysis. ''VTT Publications 478''</ref> A distinction can be made between '''static method adaptation''' and '''dynamic method adaptation'''.<ref name="Aydin2005"> Aydin, M.N., Harmsen, F., Slooten van K., & Stegwee, R.A. (2005). On the Adaptation of An Agile Information Systems Development Method. ''Journal of Database Management Special issue on Agile Analysis, Design, and Implementation, 16(4),'' 20-24 </ref> 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 is not 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).<ref name="Aydin2005"> Aydin, M.N., Harmsen, F., Slooten van K., & Stegwee, R.A. (2005). On the Adaptation of An Agile Information Systems Development Method. ''Journal of Database Management Special issue on Agile Analysis, Design, and Implementation, 16(4),'' 20-24 </ref> ==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 is generally no comprehensive support.<ref name="Abrahamsson2003">Abrahamsson, P., Warsta, J., Siponen, M.T., & Ronkainen, J. (2003). New Directions on Agile Methods: A Comparative Analysis. ''Proceedings of ICSE'03'', 244-254.</ref> [[PRINCE2]] has been suggested <!-- by whom? --> as a suitable, complementary project management system.<ref name="Prince2DSDM"> Agile Alliance at [http://agilealliance.org/system/article/file/904/file.pdf http://agilealliance.org/system/article/file/904/file.pdf ]: :''PRINCE2 (Projects in Controlled Environments) . . . is a project management method that was specifically designed to be generic and independent of any particular project type or development method. As with DSDM,its use is dramatically on the increase in both the public and private sectors. As a development method and a project management method, the two should be complementary. Some have perceived the dynamic emphasis of DSDM and the control emphasis of PRINCE2 to be in conflict. However, this is not the case. When DSDM was being developed, those involved had PRINCE firmly in mind. This is reflected in a number of the DSDM principles and techniques – for example, product-based planning, the involved partnership of users and developers, and the strong emphasis on the underlying business case.''</ref> ==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: [[Revision control|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, acunote, ppts, [[Mingle]], [[Gatherspace]] and visionproject. ==Agile methods== Some of the well-known agile software development methods: *[[Scrum (development)|Scrum]] *[[Agile Modeling]] *[[Agile Unified Process]] (AUP) *[[Agile Data Method]] *[[Test Driven Development]] (TDD) *[[Feature Driven Development]] (FDD) *[[Behavior Driven Development]] (BDD) *[[Essential Unified Process]] (EssUP) *[[Extreme programming]] (XP) *[[DSDM]] Other approaches: *[[Software Development Rhythms]] *[http://www.agilemodeling.com/essays/agileDocumentation.htm Agile Documentation] *[[Microsoft Solutions Framework]] (MSF) *[[Database refactoring]] ==Agile best practices== *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 ==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)[http://jroller.com/page/bokmann?entry=improving_your_processes_aim_high] score projects against a number of agility factors to achieve a total. The similarly-named Agility Measurement Index [http://doi.acm.org/10.1145/1185448.1185509], scores developments against five dimensions of a software project (duration, risk, novelty, effort, and interaction). Other techniques are based on measurable goals [http://www.smr.co.uk/presentations/measure.pdf]. Another study using fuzzy mathematics<ref name="Kurian 2006">Kurian, Tisni (2006). "Agility Metrics: A Quantitative Fuzzy Based Approach for Measuring Agility of a Software Process" ''ISAM-Proceedings of International Conference on Agile Manufacturing'06(ICAM-2006)'', Norfolk, U.S.</ref> 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== [[Extreme Programming]]'s initial buzz and controversial tenets, such as [[pair programming]] and [[continuous design]], have attracted particular criticism, such as McBreen<ref name="mcbreen">{{cite book|last=McBreen|first=P.|title=Questioning Extreme Programming|publisher=Addison-Wesley|location=Boston, MA|year=2003|id=ISBN 0-201-84457-5}}</ref> and Boehm and Turner.<ref name="boehm2004"/> Many of the criticisms, however, are believed by Agile practitioners to be misunderstandings of agile development.<ref name="sdmagazine1811">[http://www.sdmagazine.com/documents/s=1811/sdm0112h/0112h.htm sdmagazine]</ref> In particular, [[Extreme Programming]] is reviewed and critiqued by Matt Stephens's and Doug Rosenberg's ''Extreme Programming Refactored''.<ref name= "ExtremeProgrammingRefactored" >[http://www.softwarereality.com/ExtremeProgrammingRefactored.jsp Extreme Programming Refactored]</ref> 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.<ref name= "TheGreatPyramidOfAgile" >[http://worsethanfailure.com/Articles/The-Great-Pyramid-of-Agile.aspx The Great Pyramid of Agile]</ref> ==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]]) do not mean the same thing in practice, even though they are 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]] - i.e., 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 is 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 is 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<!-- better links to reports needed; also need clarification of which conferences were peer-reviewed and which have academic credentials -->: * XP (2000<ref>[http://ciclamino.dibe.unige.it/xp2000/ 2000]</ref>, 2001, 2002, 2003, 2004, 2005, 2006<ref>[http://virtual.vtt.fi/virtual/xp2006/ 2006]</ref>) * XP Universe (2001<ref>[http://www.xpuniverse.com/2001/xpuPapers.htm 2001]</ref>) * XP/Agile Universe (2002,<ref>[http://www.xpuniverse.com/2002/schedule/schedule 2002]</ref>2003,<ref>[http://www.xpuniverse.com/2003/schedule/index 2003]</ref> 2004<ref>[http://www.xpuniverse.com/2004/schedule/index 2004]</ref>) * Agile Development Conference (2003,<ref>[http://www.agiledevelopmentconference.com/2003/schedule/experiencereports.html 2003]</ref> 2004,<ref>[http://www.agiledevelopmentconference.com/schedule/expreports.html 2004]</ref>) (peer-reviewed; proceedings published by IEEE?) * Agile (2005,<ref>[http://www.agile2005.com/track/experience_reports 2005]</ref> 2006) (peer-reviewed; proceedings published by IEEE) == Agile Project Management and EVM == [[Earned Value Management]] is a PMI ([[Project Management Institute]]) approved project management technique to objectively measure the success of a project based on the following 3 parameters *Cost of the project: Over or Under Budget *Schedule to implement the project: On time or delayed delivery *Technical Performance in the project: Amount of technical work accomplished An integrated and weighed measurement of these 3 parameters is compared to PV (Planned Value) to determine the health of the project. The cost efficiency, schedule efficiency of the project can be calculated using EV and hence the project manager (and other stakeholders) can get early warnings on time to complete and cost to complete the project. Arguably, EVM does not measure project quality, so it is possible for EVM to indicate a project is under budget, ahead of schedule and scope fully executed, but still have unhappy clients due to poor product quality. Agile does not come with such well defined metrics as EVM; burn down and burn up charts help the agile project teams to analyze and monitor the scope and quality of the projects without giving much view to the costs involved. Agile EVM can be used to measure some form of costs for an agile project at the end of an iteration to give the project manager one more metrics to analyze the project health. Planned Value (or PV) for a Scrum project can be the estimated value of the work planned to be completed on a certain date; e.g., estimated story points for all the ‘features’ to be completed till the release date. Earned Value (EV) on the other hand is the actual value of work completed on the same date as PV; e.g., sum of the estimated story points completed till the release date. (Please don’t confuse business value or dollar value with EV here; Actual Cost is the actual dollars spend to complete a set of features) The key metrics to consider while calculating Agile EVM *Number of iterations completed (and number of planned iterations in a release) *Total count of story points considered ‘done’ (and total number of story points for a given release) *Total number of story points added/removed to the release *Planned total budget for completing t he release (and actual cost incurred) Scenario 1: Let us consider an example to arrive at the correct figures for these metrics. A project with a total budget (or Budget at Complete BAC) of $ 120,000 and consisting of 4 planned iterations (for a release) is at the end of Iteration 1. The product backlog looks like this when arranged in the order of priority for 4 iterations (target velocity of 28 story points per iteration) {| class="wikitable" |- ! Story Definition ! Story Points Estimated ! Targeted Iteration ! Completed Y/N ! Actual Dollar Cost |- | Story 1 | 10 | 1 | Y | 11000.00 |- | Story 2 | 8 | 1 | Y | 8300.00 |- | Story 3 | 9 | 1 | Y | 10750.00 |- | Story 4 | 15 | 2 | N | |- | Story 5 | 12 | 2 | N | |- | Story 7 | 8 | 3 | N | |- | Story 8 | 8 | 3 | N | |- | Story 6 | 10 | 3 | N | |- | Story 9 | 10 | 4 | N | |- | Story 11 | 12 | 4 | N | |- | Story 10 | 8 | 4 | N | |- | '''Total Story Points: ''' | '''110''' | '''Completed Story Points: ''' | '''27''' | '''30050.00''' |} '''Planned Value''' for Iteration 1 (Expected Percent Complete * Total Budget): 25% of 120,000.00 = $ 30,000.00 '''Actual Percent Complete''' for Iteration 1 (Total Number of Completed Story Points / Total Story Points): 27/110 = 24.5% '''Earned Value''' (Actual Percent Complete * Total Budget): 24.5 * 120,000.00 = $ 29,400.00 So the Earned Value (EV) for the Iteration 1 is less than the Planned Value and hence the project will need more monitoring and control from the team for the remaining iterations. Once EV is calculated correctly (based on the available data), the EV can be used to determine the cost efficiency and schedule efficiency of the project. These are 2 key metrics to determine whether the project will complete on time and on budget. '''CPI (Cost Performance Index)''' measures how efficiently the team is spending money against the targeted dollar cost. For our project sample, actual cost (AC) for Iteration 1: 30,050.00 [[Cost Performance Index]] is the ratio of the EV to Actual Cost i.e. 29,400 / 30,050 = .97 CPI of less than 1 means that the EV is less than AC or that the project is over budget. The team is actually spending more money than was initially planned for. A CP I value of 1 or less than 1 is always the target for any project team. For our sample project the CPI is .9 which is very near to 1 though less than 1 and we can conclude that the project is running slightly over budget at the end of iteration 1. The CPI value can be used to determine the '''Estimate at Complete''' which is basically the forecast of the total dollar amount needed to complete the project (if the CPI remains constant). While this amount is not the most accurate value to trust, it is accurate enough to identify trends in time to take corrective action. Estimate At Complete (EAC)= BAC / Cost Performance Index. e.g., Estimate at Complete is $ 120,000 / .97 = $ 123,711 (approximately 3% budget overshoot) '''SPI (Schedule Performance Index)''' allows the team to analyze whether the project is behind schedule with respect to the final delivery commitments. [[Schedule Performance Index]] is calculated as a ratio of EV and PV. So in our project at the end of Iteration 1, the SPI is 29,400/ 30,000 = .98. Similar to CPI, SPI of less than 1 means that the EV is less than PV or that the project is under schedule. A SPI value of 1 or less than 1 is always the target for any project team. SPI can be also used to calculate the Estimate Time to Complete. Estimate To Complete (ETC): Total Number of Planned Iterations/ SPI e.g., Estimate Time to Complete is 4/.9 = 4.4 (almost an extra iteration to complete) Since all the values are based on estimated story points and how many story points actually gets completed, EVM may be calculated at the end of each iteration to monitor the progress of the project and make the stakeholders aware of any risks associated with the project. <ref>http://en.wikipedia.org/wiki/Earned_value_management </ref> <ref>http://www.infoq.com/articles/agile-evm</ref> ==See also== *[[Agile web development]] *[[Software Engineering]] *[[Extreme programming]] *[[Collaborative software development model]] *[[Software Development Rhythms]] ==References== <!--<nowiki> See http://en.wikipedia.org/wiki/Wikipedia:Footnotes for an explanation of how to generate footnotes using the<ref> and </ref> tags </nowiki>--> {{reflist|2}} ==Further reading== *Fowler, Martin. [http://www.martinfowler.com/articles/designDead.html ''Is Design Dead?'']. Appeared in ''Extreme Programming Explained'', G. Succi and M. Marchesi, ed., Addison-Wesley, Boston. 2001. *Riehle, Dirk. [http://www.riehle.org/computer-science/research/2000/xp-2000.html ''A Comparison of the Value Systems of Adaptive Software Development and Extreme Programming: How Methodologies May Learn From Each Other'']. Appeared in ''Extreme Programming Explained'', G. Succi and M. Marchesi, ed., Addison-Wesley, Boston. 2001. *Tomek, Ivan. [http://www.whysmalltalk.com/articles/tomek/teachingxp.htm ''What I Learned Teaching XP''] *M. Stephens, D. Rosenberg. ''Extreme Programming Refactored: The Case Against XP''. Apress L.P., Berkeley, California. 2003. (ISBN 1-59059-096-1) *D. Rosenberg, M. Stephens. ''Agile Development with ICONIX Process''. Apress L.P., Berkeley, California. 2005. (ISBN 1-59059-464-9) *Beck, et al., [http://www.agilemanifesto.org/ ''Manifesto for Agile Software Development''] *Larman, Craig and Basili, Victor R. [http://www2.umassd.edu/SWPI/xp/articles/r6047.pdf ''Iterative and Incremental Development:A Brief History '' IEEE Computer, June 2003] *Abrahamsson, P., Warsta, J., Siponen, M.T., & Ronkainen, J. (2003). New Directions on Agile Methods: A Comparative Analysis. ''Proceedings of ICSE'03'', 244-254. *Abrahamsson, P., Salo, O., Ronkainen, J., & Warsta, J. (2002). Agile Software Development Methods: Review and Analysis. ''VTT Publications 478''. *Aydin, M.N., Harmsen, F., Slooten, K. v., & Stagwee, R. A. (2004). An Agile Information Systems Development Method in use. ''Turk J Elec Engin, 12(2),'' 127-138 *Aydin, M.N., Harmsen, F., Slooten van K., & Stegwee, R.A. (2005). On the Adaptation of An Agile Information Systems Development Method. ''Journal of Database Management Special issue on Agile Analysis, Design, and Implementation, 16(4),'' 20-24 *Cohen, D., Lindvall, M., & Costa, P. (2004). An introduction to agile methods. In ''Advances in Computers'' (pp. 1-66). New York: Elsevier Science. *Karlstrom, D., & Runeson P. (2005). Combining agile methods with stage-gate project management. ''IEEE Software, 22(3),'' 43-49 *Highsmith, J. ''Agile Software Development Ecosystems''. Addison-Wesley Professional, 2002 (ISBN 0-20176-043-6) *Waldner, JB. ''Nanocomputers and Swarm Intelligence''. ISTE, 2008, (ISBN 9781847040022) ==External links== {{linkfarm}} <!--Official Web sites of founding organization, seminal documents, etc.--> *[http://www.agileManifesto.org/ Manifesto for Agile Software Development] *[http://www.agilealliance.org/ The Agile Alliance] <!--Articles, papers, essays--> *[http://martinfowler.com/articles/newMethodology.html The New Methodology] Martin Fowler's description of the background to agile methods *[http://www.pmforum.org/library/papers/2007/PDFs/DeBaar-11-07.pdf "Why Agile Popped Up on the Radar When it Did"] *[http://www.shmula.com/401/lean-for-software/ Interview on Lean for Software Methods] *[http://software-quality.blogspot.com/2006/10/risk-based-selection-for-agile.html Risk based selection for agile iterative lifecycle methods] *[http://www.acmqueue.com/modules.php?name=Content&pa=showpage&pid=110 "The Demise of the Waterfall Model Is Imminent" and Other Urban Myths] *[http://www.gatherspace.com/static/scope_creep.html Managing Scope Creep using Agile Iterations] *{{cite news|url=http://www.ddj.com/dept/architect/193402902|title=10 Mistakes in Transitioning to Agile: Slow down the transition in order to go fast|author=Levent Gurses |publisher=Dr. Dobb's Journal|date=[[2006-11-01]]}} *[http://www.acmqueue.com/modules.php?name=Content&pa=showpage&pid=424 Breaking the Major Release Habit] - Why are long iterations a hard habit to break? *[http://www.techbookreport.com/SoftwareIndex.html An extensive list of book reviews on Agile topics, including practices, particular schools of Agile and software development] <!-- Volatile content: blogs, news, journals, forums--> *{{dmoz|Computers/Programming/Methodologies/Agile|Agile}} [[Category:Software project management]] [[Category:Software development philosophies]] [[Category:Agile software development| ]] [[da:Agile]] [[de:Agile Softwareentwicklung]] [[es:Desarrollo ágil de software]] [[fr:Méthode agile]] [[ko:애자일 개발 프로세스]] [[is:Agile]] [[it:Metodologia agile]] [[he:פיתוח תוכנה זריז]] [[lv:Spējā izstrāde]] [[lt:Lankstusis programavimas]] [[nl:Agile-software-ontwikkeling]] [[ja:アジャイルソフトウェア開発]] [[pl:Agile]] [[pt:Desenvolvimento ágil de software]] [[ru:Гибкая методология разработки]] [[sh:Agilni razvoj softvera]] [[fi:Ketterä ohjelmistokehitys]] [[sv:Agile software development]] [[vi:Lập trình linh hoạt]] [[uk:Гнучка розробка програмного забезпечення]] [[zh:敏捷软件开发]]