User stories, over exhaustive requirements

It's easy to aim to capture all the requirements at the same time but, in an uncertain world, this is not very realistic or practical. So, the purpose of user stories is to extrapolate the same, if not more, information by cutting the requirement elicitation process in a different way.

Create narratives by consulting end users and the product owner. Describe what they need the software to do, and incrementally add more and more detail to the stories until the anticipated scenarios are covered. For non-functional requirements such as supportability and ease of maintenance, the relevant support teams will be the user.