Software Estimation: Demystifying the Black Art (Best Practices (Microsoft))

1.1 Estimates, Targets, and Commitments

Strictly speaking, the dictionary definition of estimate is correct: an estimate is a prediction of how long a project will take or how much it will cost. But estimation on software projects interplays with business targets, commitments, and control.

A target is a statement of a desirable business objective. Examples include the following:

• "We need to have Version 2.1 ready to demonstrate at a trade show in May."

• "We need to have this release stabilized in time for the holiday sales cycle."

• "These functions need to be completed by July 1 so that we'll be in compliance with government regulations."

• "We must limit the cost of the next release to $2 million, because that's the maximum budget we have for that release."

Businesses have important reasons to establish targets independent of software estimates. But the fact that a target is desirable or even mandatory does not necessarily mean that it is achievable.

While a target is a description of a desirable business objective, a commitment is a promise to deliver defined functionality at a specific level of quality by a certain date. A commitment can be the same as the estimate, or it can be more aggressive or more conservative than the estimate. In other words, do not assume that the commitment has to be the same as the estimate; it doesn't.