The Symbolic Stream Generator
) is a software productivity aid by Unisys
for their mainframe computers
of the former UNIVAC 1100/2200 series
SSG is used to generate RUN-Streams (corresponding to IBM's Job Control Language), apply and administer symbolic changes to program sources as a form of version control, and for many other purposes.
An SSG program (i.e., its "job control script") is called a Skeleton, and its programming language Symstream.