1. (Software) It refers to a process, usually implemented as a software routine, at the highest level (Level 7) of the ISO open system architecture. 2. (SDS) It refers to such processes as the Battle Management, Navigation, Network Control, and other high level functions which may originate or receive messages over the SDS Communication network, via underlying lower-level protocols. 3. Software designed to fulfill specific needs of a user. 4. (Acquisition) The process of selecting requirements that are pertinent and cost effective for the particular materiel acquisition and contractually invoking them at the most advantageous times in the acquisition cycle.