Time and Effort Available.

Our ability to develop engineering estimates is constrained by time and person-power availability. In an ideal world, it would cost nothing to use unlimited resources over an extended period of time. However, reality requires the use of limited resources in fixed intervals of time. Thus for a rough estimate only limited effort is used.

Constraints on time and person-power can make the overall estimating task more difficult. If the estimate does not require as much detail (such as when a rough estimate is the goal), then time and personnel constraintsmay not be a factor.When detail is necessary and critical (such as in legal contracts), however, requirements must be anticipated and resource use planned.