In Scrum user stories are the starting point of a conversation. This articles discusses the challenge for the Product Owner to provide acceptance criteria to help the Scrum team understand user stories. The author explains that acceptance criteria need not constitute an exhaustive list, but they should be sufficient to move forward. Acceptance criteria are temporal in nature, because they are the functionality the product owner had in mind at a distant time in the past. Acceptance criteria become refined with sprint progress through each story iteration. Acceptance criteria can never be complete, as they embody expectations that change over time.
