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Reviewer: Martti J. Tienari

The definition and generation of compiler front-ends is well known and conceptually well formalized. The art of compiler back-end generation, in contrast, is much less well developed. An approach called “semantics-directed compiler generation” aims at creating the conceptual foundation for the automatic construction of compiler back-ends. The theoretical basis for this line of thought is a style of semantic definition called denotational semantics. Lee's Ph.D. thesis, printed as this MIT Press book, is a significant step forward in the art of semantics-directed compiler generation. He presents thorough and convincing criticism of the traditional style of writing denotational specifications for programming languages. In order to be convinced by Lee's presentation and to appreciate the analysis he offers, the reader should be well acquainted with the denotational approach. Lee's contribution represents a new modular style of writing denotational specifications. The ideas used in order to achieve an appealing modularity are based on earlier contributions by Mosses, Watt, and Pleban (Lee's thesis advisor). Lee specifies programming languages at two different specification levels, which he calls macrosemantics and microsemantics. Macrosemantics corresponds to the compiler front-end, while microsemantics corresponds to the compiler back-end (run time behavior) specifications. He thus deviates considerably from the classical style of writing denotational specifications. He conforms to basic denotational thinking, however, and gains the theoretical underpinnings his work requires. His apparently superb skills in engineering language specifications, programs, and the code generators needed in the experimental part of the work are impressive. Lee concludes, as the authors of a new approach usually do, with an appeal for more independent work in the direction he has taken. The appeal appears to be well motivated. The old dream of automatic compiler generation still needs some work before it can come true.