As I said in the chapter introduction, your aim at this early stage of product design is to create a list of features that define your software product. A feature is a way of allowing users to access and use your product’s functionality so that the feature list defines the overall functionality of the system. In this section, I explain how scenarios and stories can be used to help identify product features.
You should, ideally, identify product features that are independent, coherent and relevant:
Independence A feature should not depend on how other system features are implemented and should not be affected by the order of activation of other features.
Coherence Features should be linked to a single item of functionality. ...