Mary Poppendieck gave a talk on Workflow is Orthogonal to Schedule at Agile2009, during which she very neatly transitioned a schedule-focused view of work, into a flow-focussed view. At least I thought it was neat, so I’m going to try and reproduce the basic elements here, using my favourite agile workflow.
4 Week Time-box Schedule
Here we have a schedule showing an average of 4 features being delivered every 4 week time-box. Each time-box is preceded by 2 weeks understanding the next features, and a release is made every 8 weeks. Its not a bad schedule. There’s a regular release every two months which is better than a lot of projects, but it could be better.
2 Week Time-box Schedule
Now we reduced the time-box to 2 weeks, meaning that we do an average of 2 features in each time-box. This means that the preparation now takes only 1 week. Additionally, we are now releasing at the end of every time-box, which is also reduced to 1 week. Much better.
One Piece Flow
If we continue the evolution we end up working on a single feature at a time and releasing it immediately. Each feature only takes a week to build, and preparation and release times are now down to 1/2 a week. At this point, we don’t really have a schedule anymore, but a natural workflow.
Cumulative Flow Diagrams
One of the things that strikes me about the diagrams above, is that each step in the evolution transforms them more into a smooth Cumulative Flow Diagram. In fact, in the same presentation, Mary showed the following picture taken from Building the Empire State. This is the building schedule from from around 1930, and itself looks remarkably like a CFD. Another example of how we are not inventing anything new, but can learn from other industries and successes.