The Free On-line Dictionary of Computing (19 January 2023):

SEM

   The semantic specification language for COPS.

   ["Metalanguages of the Compiler Production System COPS",
   J. Borowiec, in GI Fachgesprach "Compiler-Compiler", ed
   W. Henhapl, Tech Hochs Darmstadt 1978, pp. 122-159].