agile · requirements analysis


User Stories are chunks of desired behavior of a software system. They are widely used in agile software approaches to divide up a large amount of functionality into smaller pieces for planning purposes. You also hear the same concept referred to as a feature, but the term "story" or "user story" has become prevalent in agile circles these days.

Kent Beck first introduced the term as part of Extreme Programming to encourage a more informal and conversational style of requirements elicitation than long written specifications. The essence of a story can be written on a single note card (Kent and I prefer 3" by 5"). Stories are deliberately not fleshed out in detail until they are ready to be developed, you only need enough understanding to allow prioritization with other stories.

Bill Wake came up with the INVEST mnemonic to describe the characteristics of good stories:

A common way to formulate stories is the "As a … I want … So that …" form. The "As a" clause refers to who wants the story, "I want" describes what the functionality is, "so that" describes why they want this functionality. The "so that" part provides important context to understand to help get from what the customer think they want to providing what they actually need.

Mike Cohn wrote what is now the standard book on writing user stories. To understand the roots of user stories in XP consider the white book, or the tasteful green book. In an earlier bliki entry I discuss why UseCasesAndStories are different.

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