Every place has a different way of assigning priority and/or severity to defect reports – some bigger places have many different ways (unfortunately). I’ve not been subjected to Prince2 training so here’s my take on this subject.
I reckon, the simpler the scheme, the more likely it will be used consistently. Every defect should have just a single priority/severity (call it what you will): Critical, High, Medium or Low.
- Critical – problem significantly affects ability to test the system; “showstopper” – all other work to be delayed until the issue is resolved – an example might be “unable to log in”; “screen x opens with error every time”; “function y causes my computer to explode”
- High – problem affects critical functionality; should be fixed as a matter of priority over other issues – an example would be “error x always/often occurs at process point y”
- Medium – functionality not working as per specified requirements; must eventually be fixed (at least before Go Live) – an example would be “default value not being set correctly”; “navigation does not work correctly”
- Low – cosmetic issue; “nice to have” function; or error/warning occurs very infrequently but doesn’t significantly affect correct processing; ok to Go Live if not fixed
That’s it. Notice how each category is unambiguous in what it means to the developers, testers and others. I’d expect a system to normally have mostly Medium issues, several Highs, hopefully no Criticals, and maybe some Lows. I’d expect some issues to be reclassified up or down as they are assessed, as developers negotiate with the testers and business reps.
I’m certain that there’s all sorts of great reasons why someone needs more levels, or needs to separate the “priority” concept from the “severity” or “impact” concepts, but to my mind there’s not a lot gained from forcing all your testers, developers, and change managers to learn a complicated system, and classify and update their records. When you need a 2D or 3D matrix of priority vs severity vs whatever printed and posted on your cubicle wall, it’s time to ask, “is all this really necessary?”.
Keep it simple, and everyone will not only use it, everyone else will understand it.
P.S. did you notice that Apex’s builtin “feedback” feature only has one level? It’s either a bug report, or it’s not (e.g. an enhancement request or comment). I love that.