I have two golden rules for user stories:
- The story should deliver business value: it should be meaningful to some customer, user, stakeholder. In some way the story should make their lives better.
- The story should be small enough to be delivered soon: some people say “within 2 days” but I’d generous, after all I used to be a C++ programmer, I’m happy as long as the story can be delivered within 2-weeks, i.e. the standard size of a sprint.
Now these two rules are in conflict, the need for value – and preferably more value! – pushes stories to be bigger while the second rule demands they are small. That is just the way things are, there is no magic solution, that is the tension we must manage.
Those two rules also help us differentiate between stories and epics – and tasks if you are using them:
- Epics honour rule #1, epics are very valuable but they are not small, by definition they are large this epics are unlikely to be delivered soon
- Tasks honour rule #2, they are small, very small, say a day of work. But they do not deliver value to stakeholders – or if they do it is not a big deal
Tasks are the things you do to build stories. And stories are the things you do to deliver epics. If you find you can complete a story without doing one of the planned tasks then great, and similarly not all stories need to be completed for an epic to be considered done.
In an ideal world you would not need tasks, every story would be small enough to stand alone. Nor would you need epics because stories would justify themselves. We can work towards that world but until then most teams of my experience use two of these three levels – stories and tasks or epics and stories. A few even use all three levels.
Using more than three is an administration problem. There is always a fourth level above these, the project or product that is the reason they exist in the first place. But really, three levels is more than enough to model just about anything: really small, small, and damn big.
And every story is a potential epic until proven guilty.
More about epics, stories and tasks in Little Book of Requirements and User Stories.
