Summary
Depending on devotees or dissenters, the Agile development model is all too often presented as dead-end or end-of-story. Some of that unfortunate situation can be explained, and hopefully pacified, by comparing users’ stories to plants, with their roots, trunks, and branches. Assuming that agility calls for sound footings and good springboards, it may be argued that many problems arise with stories barking at the wrong tree (application level) or getting lost in the woods (architecture level).
Application level: Trees, Bushes and Hedges
As Aristotle first stated, good stories have to follow the three unities: one course of action, located in a single space, run along continuous time.
That rule is clearly satisfied by stories that can be developed like plants growing from clearly identified roots.
Yet, stories like bushes may grow too many offshoots to be accounted for by a single action narrative; in that case it may be possible to single out a primary trunk and a set of forking branches along which different scenarii could be developed.
More serious difficulties may appear with thickets mixing offshoots from different bushes sharing the same space. That situation will first require some ground work in order to single out individual roots, and then use them to extricate each bush separately. When, like offshoots that actually mingle, story-lines cross and share actions, the description of such actions (aka features) is to be factored out and separated from the contexts of their enactment in the different story-lines.
Finally, like bushes in hedges, stories may chronicle repeated activities serving some collective purpose. That configuration is both easy to recognize and dealt with effectively by introducing a stereotyped story feature for collections and loops management.
Architecture level: Groves, Woods and Plantations
Contrary to hedges which are built on the similarity of their constituents, groves are based on their functional differences, and that can also be seen as a critical distinction between containers and architectures.
In agile parlance, that is best compared to the difference between stories and epics, the former telling what happens between users and applications, the latter taking a bird’s view of the relationships between business processes and systems.
In most of the cases the question will arise for sizable stories deemed too large for development purposes. When dealing with that situation the first step should be to look for thickets and bushes, respectively to be set apart as individual bushes or refined as scenarii. When still confronted with multiple roots, the question would be to decide between hedges and groves, that is between repeated activities and collaboration. And that decision would be critical because collaborations call for a different kind of story (aka epics or themes) set at a higher level, namely architecture.
Scaling Ups and Downs
Assuming the three-units rule cannot be met, two alternative approaches are possible, depending on whether the story has to be broken down or upgraded to an epic, and the undoing of the rule can be used to make a decision:
- When the course of actions, once started, is to be contingent on subsequent business (aka external) events the story should be upgraded to an epic, as it will often refer to a part or whole of a business process.
- Otherwise: when activities are set along different periods of time (i.e contingent on time-events) the story can be broken down depending on size, functional architecture, or development constraints.
- Otherwise: when activities are distributed across locations it may be necessary to factor out architecture-dependent features dealing with shared address spaces and synchronization mechanisms
Applying those guidelines to stories will put the whole development processes on rails and help to align requirements with their architectural footprint: business logic, system functionalities, or platform technologies.
Further Readings
- Agile between Space & Time
- The Scope of Agile Principles
- Agile vs Waterfall: Right vs Left Brain ?
- From Stories to Models
- Agile & Models
- Agile Falls
- Thinking about Practices
- Spaces, Paths, Paces (Part 1)
- Spaces, Paths, Paces (Part 2)
- Tests in Driving seats
- Projects as non-zero sum games
- Iterative Processes
The best illustration on that topic.
Thank U for this great blog,
François