Translation validation (TV) is the process of proving that the execution of a translator has generated an output that is a correct translation of the input. When applied to optimizing compilers, TV is used to prove that the generated target code is a correct translation of the source program being compiled. This is in contrast to verifying a compiler, i.e. ensuring that the compiler will generate correct target code for every possible source program - which is generally a far more difficult endeavor. This paper reviews the TVOC framework developed by Amir Pnueli and his colleagues for translation validation for optimizing compilers, where the program being compiled undergoes substantional transformation for the purposes of optimization. The paper concludes with a discussion of how recent work on the TV of software pipelining by Tristan & Leroy can be incorporated into the TVOC framework.