Good. Now that you understand the context, I want to address a concern that's been brought up recently: how do I know when to decompose my work? The short answer is always, but that's a little too ambiguous for most people. I'm going to share my guidelines here, and I'd ask that you share your advice in the comments.
Five Thresholds of Decomposition
Of course, as we decompose our work from high-level strategy (i.e. themes) to the low level work that team members execute on (i.e. stories or tasks), we rarely find that it fits neatly into 5 iterations of decomposition. Interestingly enough, that doesn't really matter. What does matter is the threshold that you establish for each level.
I'll start with User Stories, as that's the size that most people are already familiar with. Most teams have an upper-limit for how many Story Points a User Story can be in order for them to commit to it. Most of the time this is 8 points, though I've seen as high as 13 and as low as 3. Regardless, it's easy to see how the team has established a threshold for their User Stories. Whether you classify work larger than the team's threshold as a different type of work (Feature, Epic, etc.) or just call it a big User Story, the fact remains that it does not fit within the threshold for that level of planning. It must be decomposed.
Let's say that anything larger than 13 points is a Feature - but to what threshold? I would recommend something that can be done within 3 Sprints or less. Features are the lowest level of value as seen from the end-user's perspective, and end-to-end value should be production-ready with no more than 3 Sprints of development, depending on the product.
If your team's average velocity is 42, then your upper threshold for Features would be 126. That number's a little too precise for me, so let's call it 100. As Features become high priority, they should be broken into User Stories and prioritized for the coming Sprints' Planning ceremonies. Until that time, however, there is no need to decompose lower than the 100 point threshold.
Let's call Epics anything that take a quarter or less to deliver. This would be 13 weeks, so let's be conservative and call that six Sprints. We're now looking at 252 points, which can be rounded to 200, 250, or 400, depending on the scale you prefer. We now know that the work we're considering doing within the next quarter or two should be broken down into Epics that are within that threshold. While Epics may logically be broken down to under 100 points, we shouldn't feel compelled to split Epics that are already under our Epic threshold until they're a month or two out.
Anything larger than an Epic could be considered a Theme, with no upper-limit. You may decide that even Themes need an upper limit, but I generally don't include that in my recommendations.
|This blog is more what you'd call guidelines than actual rules.|
As I stated previously, these are simply guidelines. You may take a totally different approach. I find that some areas may define a Feature as something that takes two teams 4 weeks to do, knocking the threshold up to over 300. Others may decide that 100 is their Epic threshold. However you decide to define them, using thresholds as part of your working agreements make it very easy to tell when work needs to be decomposed and when it's better to wait so as to avoid rework or unnecessary work.