A promise of a further conversation
|The user story should be self-contained, in a way that there is no inherent dependency on another user story
|User stories, up until they are part of an iteration, can always be changed and rewritten
|A user story must deliver value to the end user
|You must always be able to estimate the size of a user story
|User stories should not be so big as to become impossible to plan/task/prioritise with a level of certainty
|The user story or its related description must provide the necessary information to make test development possible
"The exact number of candies in this jar can not be determined by looking at it, because most of the candies are not visible. The amount can be estimated by presuming that the portion of the jar that cannot be seen contains an amount equivalent to the amount contained in the same volume for the portion that can be seen" http://en.wikipedia.org/wiki/Estimation
Linguist Geoffrey Pullum stated the quotation was "completely straightforward" and "impeccable, syntactically, semantically, logically, and rhetorically. There is nothing baffling about its language at all."
The separation of the estimation of effort from the estimation of duration
"Every year there is a new estimation technique. The real Agile approach would be to throw estimates out"
Ron Jeffries - Agile Manifesto co-author