BTW - I think there're actually more dependencies:

Project scheduling requires:
  -- timekeeping ('already used' time can impact the schedule, especially if it is more than planned :(
  -- task/todolist (and phasing - lets not forget that! Very important for projects)
  -- resource allocation
  -- holiday booking

If you add it all up then the workorder would likely look like this:
1) project rep (indeed the most fundamental)
2) resource manager
3) scheduling
4) phased/categorized task/todolist (a normal tasklist simply has one phase)
5) timekeeping, holidaybooking, expenses
6) project scheduling
7) project reporting