Agile software development
Posted on: February 2, 2013 by:
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 introduced the term in 2001.
In February 2001, 17 software developers met at the Snowbird, Utah resort, to discuss lightweight development methods. They published the Manifesto for Agile Software Development 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.
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.
According to Kent Beck, the Agile Manifesto is based on twelve principles:
- Customer satisfaction by rapid delivery of useful software
- Welcome changing requirements, even late in development
- Working software is delivered frequently (weeks rather than months)
- Working software is the principal measure of progress
- Sustainable development, able to maintain a constant pace
- Close, daily co-operation 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—the art of maximizing the amount of work not done—is essential
- Self-organizing teams
- Regular adaptation to changing circumstances
In 2005, a group headed by Alistair Cockburn and Jim Highsmith wrote an addendum of project management principles, the Declaration of Interdependence, to guide software project management according to agile development methods.
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.Multiple iterations might be required to release a product or new features.
Team composition in an agile project is usually cross-functional and self-organizing, without consideration for any existing corporate hierarchy or the corporate roles of team members. Team members normally take responsibility for tasks that deliver the functionality an iteration requires. They decide individually how to meet an iteration’s requirements.
Agile methods emphasize face-to-face communication over written documents when the team is all in the same location. Most agile teams work in a single open office (called a bullpen), which facilitates such communication. Team size is typically small (5-9 people) to simplify team communication and team collaboration. Larger development efforts can be delivered by multiple teams working toward a common goal or on different parts of an effort. This might require a coordination of priorities across teams. When a team works in different locations, they maintain daily contact through videoconferencing, voice, e-mail, etc.
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 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.
Most agile implementations use a routine and formal daily face-to-face communication among team members. This specifically includes the customer representative and any interested stakeholders as observers. 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. This face-to-face communication exposes problems as they arise. “These meetings, sometimes referred as daily stand-ups or daily scrum meetings, are held at the same place and same time every day and should last no more than 15 minutes. Standing up usually enforces that rule.”
Agile development emphasizes working software as the primary measure of progress. This, combined with the preference for face-to-face communication, produces less written documentation than other methods. The agile method encourages stakeholders to prioritize “wants” with other iteration outcomes, based exclusively on business value perceived at the beginning of the iteration (also known as value-driven).
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 methodology is to be flexible, sensible and to focus on getting stuff done.
In agile software development, an information radiator is a (normally large) physical display placed in a prominent location in an office, where passers-by can see it, and which presents an up-to-date summary of the status of a software product or products. The name was coined by Alistair Cockburn, and described in his 2002 book Agile Software Development. A build light indicator may be used to inform a team about the current status of their project.
Well-known agile software development methods include:
- Agile Modeling
- Agile Unified Process (AUP)
- Rational Unified Process (RUP)
- Crystal Clear
- Crystal Methods
- Dynamic Systems Development Method (DSDM)
- Extreme Programming (XP)
- Feature Driven Development (FDD)
- Kanban (development)
- Lean software development
- Velocity tracking
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).
- Kent Beck; et al. (2001). “Manifesto for Agile Software Development”. Agile Alliance. Retrieved 14 June 2010.
- Kent Beck, Mike Beedle, Arie van Bennekum, Alistair Cockburn, Ward Cunningham, Martin Fowler, James Grenning, Jim Highsmith, Andrew Hunt, Ron Jeffries, Jon Kern, Brian Marick, Robert C. Martin, Stephen J. Mellor, Ken Schwaber, Jeff Sutherland, and Dave Thomas
- Beck, Kent; et al. (2001). “Principles behind the Agile Manifesto”. Agile Alliance. Archived from the original on 14 June 2010. Retrieved 6 June 2010.
- Anderson, David (2005). “Declaration of Interdependence”.
- Beck, Kent (1999). “Embracing Change with Extreme Programming”. Computer 32 (10): 70–77. doi:10.1109/2.796139.
- Gauthier, Alexandre (17 August 2011). “What is scrum”. Planbox.
- “Daily Stand-up Meeting”. Planbox.
- Sliger, Michele; Broderick, Stacia (2008). The Software Project Manager’s Bridge to Agility. Addison-Wesley. p. 46. ISBN 0-321-50275-2.
- Cockburn, Alistair. “Information radiator”.
- Ambler, Scott (12 April 2002). Agile Modeling: Effective Practices for EXtreme Programming and the Unified Process. John Wiley & Sons. pp. 12, 164, 363. ISBN 978-0471202820.
- Abrahamsson, P., Salo, O., Ronkainen, J., & Warsta, J. (2002). Agile Software Development Methods: Review and Analysis. VTT Publications 478