Agile software development

There are a number of agile software development methods; most attempt to minimize risk by developing software in short timeboxes, called iterations, which typically last one to four weeks. Each iteration is like a miniature software project of its own, and includes all of the tasks necessary to release the mini-increment of new functionality: planning, requirements analysis, design, coding, testing, and documentation. While an iteration may not add enough functionality to warrant releasing the product, an agile software project intends to be capable of releasing new software at the end of every iteration. In many cases, software is released at the end of each iteration.

Agile methods emphasize real-time communication, preferably face-to-face, over written documents. Most agile teams are located in a bullpen and include all the people necessary to finish software. At a minimum, this includes programmers and their "customers" (customers are the people who define the product; they may be product managers, business analysts, or actual customers). The bullpen may also include testers, interaction designers, technical writers, and managers.

Agile methods are sometimes characterized as being at the opposite end of the spectrum from "plan-driven" or "disciplined" methodologies. This distinction is misleading, as it implies that agile methods are "unplanned" or "undisciplined". A more accurate distinction is to say that methods exist on a continuum from "adaptive" to "predictive". Agile methods exist 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.

The most important factor is probably project size. As size grows, face-to-face communication becomes more difficult. Therefore, most agile methods are more suitable for projects with small teams, with fewer than 20 to 40 people

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