A phase coined by TimM when at Dashboards to convey how UserStories are not complete or precise. They act as coarse grained requirements that can be estimated, but only when they are selected in an iteration do you take the time to actually nail down the details. Thus you defer the cost of filling them in, until you actually need it.
Paul remembers this works well, because the detail requirements always change based on what has been delivered to date. That's why top-down analysis and scope creep go hand in hand.
JustInTimeRequirements