At the end of each phase, a well defined set of
"deliverables" should be produced. These typically include drawings,
calculations, computer models, cost estimates, economic analyses, etc.
Since the development of the next phase is based
on these deliverables, approval to proceed to the next project phase
should be contingent upon acceptance and approval of ALL deliverables
from the previous phase. Failure to do so virtually guarantees recycle
and lost time and cost in the subsequent phase.
Similarly, subsequent changes to even small
details in these "previous phase" deliverables will have a domino
effect on current phase deliverables. As the project proceeds, it
becomes more and more difficult to "improve" the design, since the cost
and delay caused by changes becomes progressively greater.
As the PERA model indicates there are also
interfaces within the phase. At the highest level, these are between
the three main enterprise components ( Production Facilities, People,
and Control and Information Systems). However, each of these is
typically further sub-divided on large projects. The number of
sub-divisions increase as the project progresses (and staffing
increases). This is necessary to bring additional resources and skills
to bear, however each additional interface presents communication
barriers which are perhaps the most difficult aspect of large project
Most experienced project managers have an
intuitive appreciation of the nature of this problem, however a better
understanding of the reasons behind it can help minimize its effects.
These are explained in a tutorial
which is based on the principles explained in Dr Tsu's book.