In agile principles, timeboxing allocates a fixed and maximum unit of time to an activity, called a timebox, within which planned activity takes place. It is used by agile principles-based project management approaches and for personal time management. In project management Timeboxing is used as a project planning technique. The schedule is divided into a number of separate time periods (timeboxes), with each part having its own deliverables, deadline and budget. Sometimes referred to as schedule as independent variable (SAIV). "Timeboxing works best in multistage projects or tasks that take little time and you can fit them in the same time slot. It is also worth implementing in case of duties that have foreseeable time-frames of completion." As an alternative to fixing scope In project management, there are generally considered to be three constraints: time (sometimes schedule), cost (sometimes budget), and scope. (Quality is often added as a fourth constraint---represented as the middle of a triangle.) The assumption is that a change in one constraint will affect the others. Without timeboxing, projects usually work to a fixed scope, in which case when it becomes clear that some deliverables cannot be completed within the planned timescales, either the deadline has to be extended (to allow more time to complete the fixed scope) or more people are involved (to complete the fixed scope in the same time). Often both happen, resulting in delayed delivery, increased costs, and often reduced quality (as per The Mythical Man-Month principle). With timeboxing, the deadline is fixed, meaning that the scope would have to be reduced. As this means organizations have to focus on completing the most important deliverables first, timeboxing often goes hand-in-hand with a scheme for prioritizing of deliverables (such as with the MoSCoW method). To manage risk Timeboxes are used as a form of risk management, to explicitly identify uncertain task/time relationships, i.e., work that may easily extend past its deadline. Time constraints are often a primary driver in planning and should not be changed without considering project or sub-project critical paths. That is, it's usually important to meet deadlines. Risk factors for missed deadlines can include complications upstream of the project, planning errors within the project, team-related issues, or faulty execution of the plan. Upstream issues might include changes in project mission or backing/support from management. A common planning error is inadequate task breakdown, which can lead to underestimation of the time required