Wednesday, July 18, 2007

The Lack of Difference between Priority, Severity, and Urgency

Chapter 7 of Practical Development Environment discusses tracking bugs. This article expands on ideas about bug priorities from there. The short version is "life is simpler if you rename all your priority fields to show who cares about one."

The strip is from Hans Bjordahl's very funny Bug Bash site.

Priority, Severity, Urgency, ... huh?

Most bugs have a field to indicate how serious the bug is. A common series of values goes something like this:
  • 1 - The bug stops the product, and no workaround is possible
  • 2 - The bug stops the product, but a workaround is possible
  • 3 - The bug breaks a minor part of the product
  • 4 - The bug is cosmetic or an irritation
To make this field useful, you have to make it really easy for users to find out what each value is supposed to mean, right when they are entering the bug. Some people expect higher values to mean that the bug is more important. Some bug trackers provide tiny little icons to confuse you still further because you can't remember what each icon means.

Where's that Thesaurus?

But there are more serious problems with this field in practice. The first problem is that English has a lot of words for some rather similar ideas. Quick, does "priority" mean the same as "importance"? What's the difference between "urgency" and "severity"? If English is not a user's first language, this makes using your bug tracker much harder work. Yes, the words do have specific meanings but if you have to stop and think about those meanings, then they're not good words to use. My suggestion is to pick one word and use it exclusively. I'm going to use "Priority" for the rest of this discussion, but you can choose your own favorite.

Priority for Who?

"But that's not right!"you mutter, "priority doesn't mean the same as urgency." Well, actually, I think it does, depending on who's priority we're referring to. For instance, the priority of a particular bug for the engineering team is a totally different thing from the priority of the very same bug for a Sales Engineer on site with a customer breathing down their neck. The different words usually mean priority for different groups of people. If they really do mean different things, then make it more obvious. For instance, use "Due Date" instead of "Urgency" to make the sense of time explicit.

My key suggestion is to have multiple priorities for a bug but name them per team. For example, the fields could be Development Priority, QA Priority, Support Priority, and so on. You can even have a "CFO Priority" for bugs that are stopping a contract being signed at the end of a quarter. That way, everyone gets to record which bugs really matter to them, and then they can work out which ones get worked on first. And as a side benefit, no-one gets offended when their favorite bug's priority is reduced to "Minor".

Of course, this approach means that the leaders of the teams involved in producing the product have to talk to each other regularly about what they actually want the teams to work on. Call me crazy, but that seems like a good idea to me.

Priorities that are set by Customers

One last thought: some companies allow customers to enter a priority when filing a bug. This usually becomes a "how irritated are you right now?" field. Which is useful data, but perhaps not what you originally expected to record in that field. However, when you change the value of the customer's Prioritity field, it's always a problem. If you increase the severity, the customer worries whether the problem is perhaps part of a bigger issue. If you decrease the severity, you appear to be minimizing his distress. If you provide this kind of field for customers, I suggest you allow them change the values themselves.

1 comment:

Matt Doar said...

This article was referred to from�

"In Nic's example, there would be a field "User Priority" but I guess what I missed is the concept of the number of people affected. The real problem is working out how to combine the different priorities and numbers of people into a decision about what to work on next."