In computing TMG (TransMoGrifier) is a recursive descent compiler-compiler developed by Robert M. McClure and presented in 1965. TMG ran on systems including OS/360 and early Unix. It was used to build EPL, an early version of PL/I. The recursive descent algorithm of TMG was studied formally by Alexander Birman and Jeffrey Ullman. The formal description of the algorithms was named TMG recognition scheme (or simply TS).