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.
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 (time-boxes) 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 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 to 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 the 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 tests, 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 a 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.
We follow these principles behind the Agile Manifesto:
- Our highest priority is to satisfy the customer through early and continuous delivery of valuable software.
- Welcome changing requirements, even late in development. Agile processes harness change for the customer’s competitive advantage.
- Deliver working software frequently, from a couple of weeks to a couple of months, with a preference to the shorter timescale.
- Business people and developers must work together daily throughout the project.
- Build projects around motivated individuals. Give them the environment and support they need, and trust them to get the job done.
- The most efficient and effective method of conveying information to and within a development team is face-to-face conversation.
- Working software is the primary measure of progress.
- Agile processes promote sustainable development. The sponsors, developers, and users should be able to maintain a constant pace indefinitely.
- Continuous attention to technical excellence and good design enhances agility.
- Simplicity–the art of maximizing the amount of work not done–is essential.
- The best architectures, requirements, and designs emerge from self-organizing teams.
- At regular intervals, the team reflects on how to become more effective, then tunes and adjusts its behavior accordingly.