In XP, we think of requirements of coming in the form of user stories. It would be easy to mistake the
story card for the “whole story,” but Ron Jeffries points out that stories in XP have three
components: Cards (their physical medium), Conversation (the discussion surrounding them), and
Confirmation (tests that verify them).
A pidgin language is a simplified language, usually used for trade, that allows people who can’t
communicate in their native language to nonetheless work together. User stories act like this. We
don’t expect customers or users to view the system the same way that programmers do; stories act
as a pidgin language where both sides can agree enough to work together effectively.
But what are characteristics of a good story? The acronym “INVEST” can remind you that good
stories are:
• I – Independent
• N – Negotiable
• V – Valuable
• E – Estimable
• S – Small
• T – Testable
Independent
Stories are easiest to work with if they are independent. That is, we’d like them to not overlap in
concept, and we’d like to be able to schedule and implement them in any order.
We can’t always achieve this; once in a while we may say things like “3 points for the first report,
then 1 point for each of the others.”
Negotiable… and Negotiated
A good story is negotiable. It is not an explicit contract for features; rather, details will be co-created
by the customer and programmer during development. A good story captures the essence, not the
details. Over time, the card may acquire notes, test ideas, and so on, but we don’t need these to
prioritize or schedule stories.
