Every milestone is part of a set. This allows us to trigger the entire set at once, rather than each milestone seperately.
Each milestone must have a title.
Interval (in days)
Milestones always need to be defined as some point in time in relation to another point in time. For milestones, those two points in time are the reference date and the expected date. Both the reference date and the milestone date are set when a milestone instance is created. The interval - the distance between the reference date and the milestone date - is set in the milestone definition.
The process definition
For each milestone, we must specify what process definition is used to trigger it.
For each miles, we must specify what task must be completed before we consider the milestone reached.