Question

Assuming the global development effort is known (from a preliminary work structure breakdown), what percentage of that effort should I add in order to allocate enough manpower for requirement definition and refinement?

Answer 1

Requirement definition should be just that. In my experience people tend to envision the future solution already and start to put design assumptions into the requirement specifications. This unnecessarily prolongs the phase with lots of workshops and discussions. If you keep it strict to pure functional and non-functional requirement gathering (not design) I would put no more than 10%-15% of the time into it and no more than 10% of manpower effort. In your situation it seems like there are certain design descission already made and agreed to. However I would still see 10-15% because having the requirements formally put down and signed off are of good value in the project being referred back to all along the way. I once took over a project where all the personal for later phases was already recruited and burned down costs so I had to live with it. In that case I had to assume more effort (but not time) for that phase because I just did not want to skip it or skimp the phase and had the high burn rate as a fact. In project management sometimes external conditions ask for alot of flexibility and seldom all is perfect. It is also not seldom that you get assigned a certain budget as a share from a global budget and have to live with it. Often the milestones are also set. Like “do it in one year”. So time is 10-15%. Effort should be less.