Common Desktop Environment. A common windowing scheme, based on the X11 Motif system, used both in Solaris and HP-UX, to provide a similar look and feel for users.
The GUI part of COSE (q.v.) is CDE, the Common Desktop Environment which includes hypertext help, IPC (q.v.), printer support, and a bunch of other stuff. The look-and- feel is Motif-like, but there's a lot more than that to CDE. It looks like CDE certification will be withheld from most (if not all) PIGUIs since CDE includes its own API -- you have to comply with the API to be certified.