Systems Engineering FAQ

Answers by Robert Halligan FIE Aust CPEng IntPE(Aus).

I developed a value model with a weights and a value function for each Measure of Effectiveness (MOE). I was going to use this to trade off potential solutions. A criticism I am facing is that the value model does not describe the complexity of the situation. That is, different requirements are interconnected and interrelated?


One of the criteria for a good MOE (not requirement) is that it is substantially independently valued as an outcome. The incidence of highly coupled MOEs is not frequent. When this does occur, it is inevitable for one of two reasons:

  • the two MOEs are contributors to the real MOE. An example would be Reliability and Maintainability, where the real concern is Availability, e.g. with a bank and an ATM; or
  • there is double-counting in the MOEs, e.g. Life Cycle Cost and Development Cost.

The usual number of MOEs necessary to capture most of the tradeable value beyond requirements is few, from 5 to 15 or so. I wonder if the complexity of solution relationships is being mistaken for complexity of value relationships.


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Systems engineering thought leader, consultant, trainer and coach, impacting people's lives on six continents.
Published 2 years ago


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