635 A LANGUAGE FOR SEMANTIC ANALYSIS J. Cai, May 1993 Semantic analysis is important for compilers. In the APTS program transformation system, semantics is specified by rules in the language RSL. The semantic rules are interpreted by APTS to generate the semantic information of the program, which is then used by the rewriting engine for program translation. This approach has proved to be convenient and powerful in our construction of a SETL-to-C compiler. In this paper, we discuss the features, applications, implementation strategy, and performance of RSL.