48 CFR § 11.101 - Order of precedence for requirements documents.
(a) Agencies may select from existing requirements documents, modify or combine existing requirements documents, or create new requirements documents to meet agency needs, consistent with the following order of precedence:
(1) Documents mandated for use by law.
(2) Performance-oriented documents (e.g., a PWS or SOO). (See 2.101.)
(3) Detailed design-oriented documents.
(4) Standards, specifications and related publications issued by the Government outside the Defense or Federal series for the non-repetitive acquisition of items.
(b) In accordance with OMB Circular A-119, “Federal Participation in the Development and Use of Voluntary Consensus Standards and in Conformity Assessment Activities,” and Section 12(d) of the National Technology Transfer and Advancement Act of 1995, Pub. L. 104-113 (15 U.S.C. 272 note), agencies must use voluntary consensus standards, when they exist, in lieu of Government-unique standards, except where inconsistent with law or otherwise impractical. The private sector manages and administers voluntary consensus standards. Such standards are not mandated by law (e.g., industry standards such as ISO 9000, and IEEE 1680).