Extreme Programming (XP) is a software engineering methodology, the most prominent of several agile software development methodologies. Like other agile methodologies, Extreme Programming differs from traditional methodologies primarily in placing a higher value on adaptability than on predictability. Proponents of XP regard ongoing changes to requirements as an often natural and often inescapable aspect of software development projects; they believe that being able to adapt to changing requirements at any point during the project life is a more realistic and better approach than attempting to define all requirements at the beginning of a project and then expending effort to control changes to the requirements.