Timeboxes are widely used in agile and non-agile projects. The idea is that scope is (or should be) limited to the amount that is feasible within the given timeframe.

The assumption is that the team is capable of limiting itself to tasks that can be completed within the timebox. But what happens when the teams discovers that a specific task can not be completed?

There are several options:

  1. Continue the task until the end of the timebox, but do not deliver the corresponding product (because it is not finished).
  2. Continue the task but lessen the scope of the corresponding product so that the task can be finished within the timebox.
  3. Kill the task all together.

The first option might be tempting. There’s no discussion involved and nothing is scrapped. It seems to be more efficient because the task can continue the next iteration.

The problem with this approach is that there is no real deadline to meet. It really does not matter if something is not finished because you can continue in the next iteration. The same applies to the customer involved. Yes, a specific product might not be delivered at the end of the timebox because of the delays, but it will be next time.
There is no need to focus, no sense of urgency.
The timebox has become a formality, a statement within the progress report.

The timebox approach only becomes effective when the people involved feel the need to meet the deadline, again and again.
This need creates focus. The team is constantly aware of the next deadline and each decision and action is geared towards that goal.

So, options two or three are the ones to go for.

There are a couple of prerequisites though.

  • You need a “definition of done” (Scrum terminology).
    The definition of done defines as explicitly as possible the boundaries of the products delivered by the timebox.
    For instance the kind of documentation involved, whether the product is tested and how, standards to comply with, etc.
  • A quality process must be in place to confirm that products meet the criteria set by the definition of done.
  • The project manager must consistently enforce the rule that only products which meet the definition of done are delivered.
  • The customer needs to understand and comply with the consequences of definition of done.
  • A team capable of working within this process.