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The False Seductiveness of the Priority List as a Planning Tool

Andrew Elliott

Priority lists: can't escape them, can't trust them. As developers, we all make our lists: a list of issues to be triaged, a list of bugs to be fixed, a list of features to be implemented, but which to do first?

It seems so easy to just go down the list and assign a priority to each item, then to start work on one of those you have assigned the highest priority to.  BUT:

  • We often confuse importance with urgency - an urgency-based priority list will often conflict with an importance-based priority.  And both can be valid.

  • Whose priority? Yours, your client's, your co-worker's, your boss's?  A client or colleague bashing down your door may in the end be just one voice among many demanding your attention.

  • Priority/Urgency/Importance may not be visible at first glance.  A live production system bug may need to be triaged urgently, but may reveal an issue of low urgency.

  • Issues are often related to one another: often a single fix can hit several problems at once, each of which is of low importance but which taken together are a good use of effort.

  • Often a low-priority job may be tacked on to a high-priority job in a related area and so be addressed at a very low effort cost.

  • Priorities change over time: a task that may be useful to carry out today may have no value tomorrow: for example, a task needed by the month-end will increase in priority as the month progresses.

  • All this is bad enough when you are in control.  When others (e.g. clients or managers) are in charge of the prioritisation process, things can become very frustrating as irrational choices are made on the basis of indadequate information.

So, is there a more rational way of choosing which job to work on next? The two extremes are the obvious approach: highest priority first; and on the other extreme, a random choice. In practice, nobody would run their daily lives according to either these extremes: most of us would arrange things so that low priority tasks simply took a smaller slice of our attention through the day.  And so it should be with work priorities: it makes sense that even low priority jobs should receive SOME attention.

To make good choices here, you need good triage (and that deserves a write-up of its own): good decision-making needs good inputs, and it makes sense to think about what these inputs should be: a single crude "priority" rating is not enough.

I think that what is then needed is some sort of calculus of priority, whereby all the above considerations are included to work out the relative value of carrying out various jobs at different times, and an algorithm (formal or informal) that selects what items, performed when, would give the best overall result.  

Good developers have good intuitions in this regard, have some knowledge of the target system, and would unconsciously weigh these factors in comparing candidate tasks, thereby getting a “sense” of when the time was right to tackle particular jobs.   It's interesting to speculate whether this process could be assisted by smart "prioritising" tools.