Agile is a conceptual framework for software development that promotes development iterations throughout the life-cycle of the project rather than a linear approach like Waterfall. It is an iterative and incremental approach performed in a collaborative manner. There are many agile development methods and 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 may last from one to four weeks. Each iteration is an entire software project that includes planning, requirements analysis, 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 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 bullpen.