Software is best built incrementally. I hope everyone agrees with that. There’s quite a bit of disagreement as to what “incrementally”, of course, but it seems to have something to do with iterations.
No one really agrees on what an iteration is either. There are a lot of fancy metaphors and abstract phrases that get used to describe the various bits of what people think an iteration is: customers tell “stories” that engineers then “estimate”; programmers “sprint” like children at an athletics carnival; they “release” software as if it were an insufficiently randy panda; deliverables get delivered.
When one washes all of the metaphors and best little practices away, what’s left is this: build a little bit of software; evaluate it. Ideally, the software is evaluated by someone who stands to benefit directly from using it.
I’m not sure there’s much more to recent software methodologies than that. Perhaps we can explore it more in the comments.
This combination of increments and iterations spirals toward the final product, which is generally what you have left when the money runs out. Alas, if only we could draw a picture of the process with a simple spiral! When I think of it, I fall prey to a rare attack of envy toward students of hermeneutics.
The process involves spirals within spirals, cycles made up of cycles.
inwards from the greatest wheel to the smallest, the Launchpad project has:
- planning cycles
- When we plan the major features and general direction of Launchpad.
Road map sort of
stuff. Approximately six months. feature cycles
- The repeated process of beginning a feature, developing it,
fixing it, then stopping. Varies in cycle time, but usually one to three
months. release cycles
- We release whatever is in trunk each month branch cycles
- Branch from trunk, hack on it, push it up, get it reviewed, land it,
until it passes the test suite, check that the changes worked. Two or three
days. experiment cycles
- A developer is working on a thing and wants to actually see how it
in the running code. They write many tests and a fair bit of code and then
fire up a development instance of Launchpad and see how it looks. TDD cycles
- Write a failing test. Run the tests (a subset of the whole suite).
the test pass. Run the tests. Refactor. Run the tests. Probably about
Different projects surely have different kinds of cycles. Most projects probably have a subset of the ones above. In any case, thinking in terms of nested cycles is a good way of analyzing ones development process.
Each of these cycles has its own overhead and its own waste. One cycle being particularly slow has a different effect to another cycle being slow. For example, I contend that the slow branch cycle makes it less likely that trivial bugs get fixed.
Lean advocates would tell me not to think this way. They would have me unroll these cycles and lay them out on a line beginning with someone wanting something and ending with that want satisfied. They would have me draw a “value stream map”.
Bollocks to them. At least on Launchpad, we should optimize the innermost loops first.
Have I missed some kinds of cycles? Can you think of a better name than “experiment cycle”? Is there prior literature I should read? Are you going to apply these ideas to your project?