Tom's Ten Data Tips - May 2011

Time boxing

A time box is a fixed amount of time that you allocate to further progress towards some task. When you are running a project, there are three components that form an “iron triangle”: time, scope and resources. Of these three, time is most easily measured. Time boxing helps you “fit” what you can accomplish into the time you have reserved for this (the time box).

Many decisions are reached, simply by running out of time. In order to preserve voluntary control over your (perceived) priorities, a time box helps you move chunks of high urgency matter to the top of your list. That is one of the reasons why time boxing is such a powerful tool.

1. Time Boxing Leverages The Pareto Principle

Within the “iron triangle” that is formed by time, scope and resources, you need to make trade-offs between these three. Because in “real-life” so often the resources are constrained (or deemed “fixed”), what’s left is a trade-off between scope and time. Either you work to a fixed scope (set of requirements) and then ‘find out’ how long it takes, or alternatively, you may choose to optimize your output (achieve as much scope as possible) by working with fixed length iterations in order to benefit from empirical process control so that you learn how to maximize output. This is the essence of time boxing.

By ensuring that the most important, most valuable objectives are met first, you are constantly aiming to achieve 80% of remaining value using up only 20% of your resources (the Pareto principle). You keep doing this ad infinitum, and that is how you ‘squeeze’ the most value out of your resources. This is also how you track progress against your initial objectives: every time box provides another piece of empirical evidence on how far along you have come.

2. Time Boxing Helps You Decide What Can “Fit”

When resources and a deadline are fixed for your project, the only way to manage is by controlling scope. Of course you can always compromise on quality. But then, if quality is not a requirement, you can accomplish just about anything in a heartbeat. ☺ This is why Agile considers quality fixed, because if you ‘push out’ rework (a consequence of non-quality), you are never done.

To accomplish an “impossible” assignment (insufficient time & resources), you start by biting off small chunks. Time box the analysis phase – not for the entire design, merely a small initial build. Then build and test this small bit, within a short time box. Voilà, your first increment is now out of the way. Consequently, less of an assignment remains, which helps you move faster. You may time box the whole project, or parts of it. Rinse and repeat.

3. Time Boxing Forces You To Start “Somewhere”

Sometimes a new project or task may feel daunting. You wonder: “where should I start?” Truth is, there are often many places you might start. And which one is best need not necessarily matter. Or it may not matter very much. But one thing is clear: not starting doesn’t get you anywhere. ☺

Time boxing can help you prevent getting hung up in analysis paralysis. Building a prototype early helps you fail early which is a useful habit to acquire. It is extremely powerful to work “backwards” from the end result, even if the prototype was far from perfect. So get that done early. Often you just need to start somewhere. Setting a time box can provide just the jiggle you need to get started.

4. Time Boxing Helps To Drive MoSCoW

The MoSCoW acronym is most commonly associated with DSDM (Dynamic Systems Development Methodology), one of the early Agile methods. It stands for the order in which features get delivered, and prioritizes their desirability: Must, Should, Could, and Won’t have. Once you have fixed time (=time box) and budget (or: resources), your scope becomes the third and only moving variable. Within the iteration (time box) features get delivered based on this “clustering” of delivery.

In DSDM you are advised to leave about 30-40% of functionality “optional” (Could have) so the development team has maximum flexibility to include these features in the time box at a point in time when engineering practices, or specialist availability makes this most economic.

5. Time Boxing Without Support Is An Exercise In Futility (Or Frustration Tolerance…)

In order for time boxing to “work” you need to be assured you have sufficient support. A time box provides an artificial ecosystem in which you have accepted time pressure to maximize results. A team or individual commits to this challenge assuming they have access to resources. If this support proves absent, or frequent interruptions distract you from the task at hand, it just isn’t fun. Nor reasonable to accept you actually can achieve your goals. And fun helps you be creative and resourceful. So unless these base conditions are present (support), think twice before you decide to dive in. Just like you don’t dive into a pool, unless it has water in it…

6. Time Boxing Helps Keep Perfectionism In Check

Sometimes better can be the enemy of the good. Some people find it (very) difficult to accept that most of the time “good enough” really is good enough. Because a time box provides a “forced” stop to working on a given task, you must do the most important, most valuable elements first. And when your timer then goes off, you’re “done.” The sheer act of interrupting the activity provides that little bit of pressure that ensures the big rocks get in first.

7. Time Boxing Builds In ‘Pause For Thought’

After a time box has run out, you may find that a feature you are developing, or any other activity you have time boxed, has not (yet) been completed. There could be several reasons for this. Maybe it turns out the job will take (much) longer than you had foreseen. In that case the value/cost ratio has taken an unfavorable turn, and you might need to either drop this feature altogether, or reschedule it for later. And maybe you might want to rethink how you had planned to accomplish this task.

If you were almost done, that’s fine too, in that case you will probably allocate a little bit of extra time soon, to get this item from your “to do” list. This conscious addition of time to finish might also be a great safeguard against ‘over-polishing’ some important, but not mission critical bit of functionality. Just get it done, and move on (see also tip# 6).

8. Time Boxing Provides Focus

Tip# 7 has a corollary: except for giving “pause for thought” (or reconsideration), time boxing also provides focus. What we mean by this is that while you are working on your project during the iteration, you don’t need to worry about its feasibility, you don’t need to worry about its priority, you can ‘simply’ just focus on getting it done. And even without worrying when it will be done! Because in between iterations you will reconsider priorities, and your strategies for solving all the items on your backlog.

9. Time Boxing Is Great For Grunt Work

Time boxing can be used in many areas of life, either work or non-work related. If procrastination is haunting you, consider time boxing for dealing with activities that don’t appeal to you. By limiting the amount of time you ‘have’ to work on unpleasant activities (doing administration, tidying up your office, sorting out frequent flyer points, etc. – whatever you loathe), it becomes much less daunting.

This is also one of the keys to the Pomodoro technique (a time boxing variation), which limits time boxes to 25 minutes. Long enough to make some progress, but also short enough so that you might be more willing to schedule these “mini sprints.”

10. Time Boxing Can Make Resources Variable, Too!

The way time boxes are commonly used is to ‘make’ them truncate the functionality that gets delivered. This truncating is sometimes also referred to as “de-scoping.” Another way to use time boxing is by fixing time and functionality (scope), and by making resources variable. Limiting scope has proven to be more effective in managing success than making resources variable (assuming you can still fulfill the “conditions for satisfaction”).

Unfortunately, as Brooks (1975) has shown a long time ago, the correlation between resources and functionality is not quite linear. In fact, Brooks has quoted the epic phrase: “By adding resources to a late project, you make it later” which alludes to the fact that in some cases this correlation might even become negative. Which points to the key in using time boxing to vary resources: if you want to manage the scope by redistributing resources, make sure you do so in time. That is, early enough to give yourself a sporting chance of being successful…

Further reading

Some excellent books on Time boxing:

The Mythical Man-Month.
Frederick Brooks (2008)
ISBN# 0201835959