3.1 The System/Subsystem Specification (SSS) specifies the requirements for a system or subsystem and the methods to be used to ensure that each requirement has been met. Requirements pertaining to the system or subsystem's external interfaces may be presented in the SSS or in one or more Interface Requirements Specifications (IRSs) (DI-IPSC-81434) referenced from the SSS. 3.2 The SSS, possibly supplemented by IRSs, is used as the basis for design and qualification testing of a system or subsystem. Throughout this DID, the term 'system' may be interpreted to mean 'subsystem' as applicable. The resulting document should be titled System Specification or Subsystem Specification (SSS). 7.1 This Data Item Description (DID) contains the format and content preparation instructions for the data product generated by specific and discrete task requirements as delineated in the contract. 7.2 This DID is used when the developer is tasked to define and record the requirements to be met by a system or subsystem. 7.3 Requirements pertaining to system or subsystem interfaces may be presented in the SSS or in IRSs. 7.4 The Contract Data Requirements List (CDRL) (DD 1423) should specify whether deliverable data are to be delivered on paper or electronic media; are to be in a given electronic form (such as ASCII, CALS, or compatible with a specified word processor or other support software); may be delivered in developer format rather than in the format specified herein; and may reside in a computer-aided software engineering (CASE) or other automated tool rather than in the form of a traditional document. 7.5 This DID supersedes DI-CMAN-80008A and DI-IPSC-80690.