The term "stage gate," is popular in manufacturing and many project management discussions. This term along with "Milestone" is one of those vague references meant to indicate progress.
- We made it through the Design Stage Gate
- We passed the first article tested milestone
The actual notion of a Milestone, is a rock on the side of the road showing how many miles the traveler is from Rome. This "rock" assures the traveler that they are moving along the right path. Distance traveled or they're on the right road. The problem of course is the units of measure of the Milestone is usually not explicitly stated on the Milestone - the Rock kind or the Project Management kind.
The Stage Gate process is similar, with a "gate" being passed through without explicit description of what happens before the gate and after the gate.
A much better approach is to define what "done" looks like in units of measure meaningful to the stakeholder at some specific point in time for the project:
- At the Preliminary Design Review we will have 80% of the Bill of Materials identified in the Supply Chain Management system from our top 90% qualified suppliers.
- With the completion of the first Engineering Unit, we have test the vibration and shock limits in an actual working environment.
These types of descriptions describe several things Milestones and Stage Gates can never describe:
- The planned maturity of the product or service
- The units of measure for measuring this maturity
- The technical performance measure boundaries for these values - Upper and Lower boundaries
These measures speak to physical percent complete of the product or service. Milestones or Stage Gates do not. Try to avoid Milestones and Stage Gates if at all possible. Instead speak in "units of measurable increasing maturity, the boundaries of these measures, and the probabilistic behavior of these measures.
