A performance specification is a statement of requirement in terms of required results with criteria for verifying compliance, without stating methods for achieving the required results. It defines the functional requirements for the item, the environment in which it must operate, and the interface and interchangeability requirements. The opposite of a performance specification is a detail specification. A detail specification gives design solutions such as how a requirement is to be achieved or how an item is to be fabricated or constructed. Acquisition reform is striving to reduce Government risk by using performance based specifications and standards which make the contractor responsible for providing the item or services requested, assume the risk for meeting performance requirements, and seek innovations to efficiently and effectively achieve performance objectives. Past performance evaluations provide assurance of the contractor's ability to perform as required.