User Stories
User stories are one of the primary development artifacts for Scrum and Extreme Programming (XP) project teams. A user story is a very high-level definition of a requirement, containing just enough information so that the developers can produce a reasonable estimate of the effort to implement it.
In Extreme Programming a user story is a story about how the system is supposed to solve a problem or support a business process. Each user story is written on a story card, and represents a chunk of functionality that is coherent in some way to the customer.
These written cards are preserved through the entire planning and development process (Planning Game, Release Plan, Iteration Planning). They are given priorities by the customers, they are given estimates by the developers, they are broken down into engineering tasks at the time that they are scheduled for development. There are one or more acceptance tests, owned by the customers, to give them confidence that the user story has actually been completed.
A user story is an informal statement of the requirement as long as the correspondence of acceptance testing procedures is lacking. Before a user story is to be implemented, an appropriate acceptance procedure must be written by the customer to ensure by testing or otherwise determine whether the goals of the user story have been fulfilled. Some formalization finally happens when the developer accepts the user story and the acceptance procedure as his work specific order.
