Ivar Jacobson's presentation “What CMMI cannot give you: good software” features a short story about a Foolish Farmer and his Thirsty Cow.
Jacobson uses this story to help illustrate a significant difference between bad processes and good processs and to understand what CMM/CMMI is and what it is not.
It's easy to make a good process measurable; but it's hard to make a measurable process good.