Time Machine

February 26, 2019

OK, Mr. Peabody, where are we going today?

Well Sherman, Any time I explain what Scrum or XP is, I start with time boxes. The time box method has been around a really long time. The earliest record I can find in a casual search is where they were used at DuPont in the 1980s. I suspect that time boxes are much older than that. The time box basically applies a constraint to the system. It creates an arbitrary start and end date, usually on the smaller side. You commit to a fixed amount of work and when the end of the time box is reached you are done, no matter what the completion state of the work. Work that is complete is counted as done within the time box, work that still remains to be finished is either scope that gets dropped or perhaps that work is continued in the next time box.

This technique has some benefits:

  1. Deadlines, even arbitrary 2 week time boxes, help keep everyone focused.
  2. Deadlines force the question of prioritization. Not everything will fit in the box.
  3. Small time boxes create a short heartbeat or pulse that is useful for measures of capacity and throughput.
  4. It forms a useful skeleton for the OODA improvement cycle

There are also some challenges:

  1. Small time boxes demand that you figure out how to break work down into smaller, but still valuable pieces. Many teams find this hard to do.
  2. Small time boxes means that it is almost inevitable that scope won’t be delivered sooner or later. How the business manages this scenario says a lot about how the benefits of time boxes are perceived.
  3. Much of the angst of estimation is due primarily to the fact that teams are struggling to fit work to their limited capacity in ways they didn’t have to prior to the time box.
  4. It doesn’t work if you can’t break the iron triangle of scope, schedule, and quality. Scope usually has to be compromised in some form or another in order for time boxes to work (it’s kind of what they are based on)

Like so many other things, a time box is useful in the right context, but not all contexts. I’ve seen a few projects where a time box would not work (hardware constraints, legacy mainframe applications, an organization that wasn’t willing to give up the iron triangle, etc.). All too often we force the time box on the team and tell them that they suck if they can’t overcome the challenges. Sometimes that’s true, other times it isn’t. It’s a judgement call. Beware, and don’t let yourself get caught forcing a round peg into a square hole (I’m looking at you Scrum).