4. Recommended Core Techniques
4.1 Timeboxing
Traditional project management uses milestones to agree on a deliverable to a given
point in time. While milestones work well enough, a timebox is a much more
powerful tool to achieve the same result. A timebox is an interval, usually no longer
then 6 weeks, where a given set of tasks should be achieved. The reason for the
relatively low duration of timeboxes is the fact, that humans give much more accurate
estimates in the near-future involving a small set of tasks, while estimates into the
distant future involving large sets of tasks turn out to have hefty errors. Timeboxes
can contain several tasks, and at the end need to deliver a product. Milestones also
suffer from having a fixed deliverable, while timeboxes are subject to change, since
the tasks are defined, not the necessarily the deliverable, which can change if
prioritization shifts during the timebox iteration, allowing for rapid response to
business needs. In short: DSDM rather drops functionality in favor of delivering in
time.
Looking at the four timebox examples in figure 3 we can observe several important
attributes of timeboxing in combination with the DSDM project phases:
1. Timeboxes can be of different length (example 2,3 and 4)
2. Several of the same DSDM phases can be executed right after a
timebox of the same phase has finished (example 1,2 and 3)
3. Parallel timeboxes are possible, even complementary timeboxes are
allowed (example 1 and 3)
4. Different DSDM phases can be realized in one timebox at the same
time (example 1 and 3)
5. Timeboxes can be nested (examples 1, 2, 3 and 4 are nested into the
“Overall Timebox”)