Comparison
CommitmentvsEstimate
Commitment
the date went on a customer contract, and after that the scope was the only thing left to move.
A promise to deliver something by a time, made deliberately and with consequences for missing it. A commitment should be derived from an estimate with buffer, made by whoever owns the tradeoffs, and it should be far rarer than estimates are. Keeping the words distinct is one of the highest-leverage things an engineer can do in a planning conversation, because once an estimate has been repeated as a commitment it is very hard to take back.
Full entry →Estimate
you said about three weeks, and heard it repeated in a meeting as the date it will be done.
A probabilistic statement about how long something is likely to take, given what is known now. It is not a promise, and the entire dysfunction of software planning comes from the two being conflated somewhere between the engineer and the roadmap. Stating the confidence and the assumptions along with the number is what keeps it an estimate on its way up the organisation.
Full entry →