FAA STD- Preparation of Interface Documentation (2007)

2.1 Interface Documentation

The IRD and ICD are closely related and each has a specific purpose. The program office within each line of business is typically responsible for developing IRDs and ICDs IRDs identify the interface requirements between two subsystems, between a subsystem and a “user” (where the “user” can be viewed as a variable that can be filled with multiple subsystems), or between a facility and a subsystem. The requirements in an IRD are often traced to or derived from requirements in a system-level specification or system requirements document.

ICDs describe the formal agreement that documents how the interface requirements outlined in the IRD are implemented; the ICD is the as-built configuration. The design characteristics in an ICD trace to and are derived from the interface requirements in an IRD. When IRDs and ICDs are approved, they become baseline documents and are placed under configuration management. Appendix I of this document describes the development and approval process for IRDs and ICDs. The requirements in this standard shall be used to document key interfaces for FESS. If specific requirements or data are not known at the time for approval (and baseline) of the IRD, they shall be identified as ‘To Be Supplied (TBS)’. The term TBS shall not be used in an ICD unless reference is made to a future capability in a future revision. After TBS items are determined, the IRD and ICD shall be revised in a timely manner.