In optimization theory, the equation (function) to be maximized or minimized, subject to constraints.
If the concept is applied to SE, then the objective function for development is parameterized by the Measures of Requirement as allocated by way the development specification. We have to be careful with this concept, however, because it is tempting to try and actually optimize the system using the Measures, only. What we really want is to produce a value for some cost-schedule function (defined by the Acquisition Customer in the SoW or T&C) below some maximally-acceptable value prior to some maximally-acceptable date while placing the verified capability of associated CI within the region of an abstract space centered on the Measures’ nominal values and bounded by their tolerances. See also Trade Study.
As a practical matter, most Acquisition Customers are unable to determine (let alone specify) their preferences for the various types of costs and schedules.