Freezedown

The funny thing about creating a web site, web app or software project is that initially

• Everything is up for discussion, then...


• Nothing is up for discussion

This is because Project Variability is a time sensitive beast. And the best projects are ones where everyone, from the client, through the information architect to the developers and designers understand that the degree to which features are carved in stone is entirely dependent on when they are in the project lifespan.

The crux of this idea is that the tolerance for change in a project isn't an absolute - its a curve. Project's can undergo change midstream, but the tolerance a project has for change is in direct proportion to its remaining time. I call this phenomenon Freezedown: the degree to which features and implementation details are frozen in the project.

To try to express this lets compose a formula:

TV = F / T

where:

TV = Tolerable Variability: Change occurring against a feature set or implementation method.

F = Future Iterations Remaining in Project

T = Total Iterations in Project

So - lets say we had a project that was 16 weeks, broken up into 8 two-week iterations. Before the project development kicked off, there would be 8 out of 8 iterations remaining. That's "1" or 100%. At this point everything is on the table, there's no downside of changing the feature set, or the (at this point, planned) details of implementation.

As the project goes on, it can still accommodate changes, but the tolerance drops off:

• Iteration 1: 87.5%


• Iteration 2: 75%


• Iteration 3: 62.5%


• Iteration 4: 50%


• Iteration 5: 37.5%


• Iteration 6: 25%


• Iteration 7: 12.5%


• Iteration 8: Feature freeze

What do these percentages mean? They abstractly represent the amount of feature changes or implementation changes that are open for discussion. This is the tolerance of the project for change.

If something comes along that exceeds that level of change, at that time, the scope has changed - which at the very least means the original schedule is probably not going to be realistic any more. Everyone in the project should be aware of the degree of Freezedown in effect at any given point.