TWO-LEVEL GRAMMAR: AN IMPLEMENTABLE METALANGUAGE FOR CONSISTENT AND COMPLEMENTARY LANGUAGE SPECIFICATIONS.

摘要

Programming languages have traditionally been defined operationally, axiomatically or denotationally. This work introduces Two-Level Grammar (TLG) as a programming language for giving consistent and complementary definitions of programming languages in an implementable manner.;To demonstrate the capability of TLG to give consistent and complementary language specifications, a Pascal-like language with recursive procedures and recursive functions and the usual control constructs is used as a subject language. The uniqueness of this work is that this is first time a single metalanguage is being used to define languages using the three accepted methods. Moreover, TLG can specify context-free syntax, static and dynamic semantics of a programming language and these three components can be given separately to enhance modularity of the definitions.;The significance of the results is that semantics-directed implementation is made possible from an operational or a denotational definition. Since the axiomatic definition is executable, partially automated program verification within the framework of a language definition is achieved. Hence an integrated system for interpretation or verification is realizable, the components of which are derived automatically from the TLG specification of language. The advantages of TLG over other metalanguages are that it is readable, implementable and can completely specify a programming language. Therefore, it can be a convenient tool for language designers, implementors, and users.;It is shown that TLG is a functional programming language. Advantages of using the TLG as a programming language are readability and strong typing of function domains. To execute TLG specifications directly, algorithms for sequential and data flow models of interpretation of TLG's are given. TLG allows the closest to programming in natural language we have seen, and hence TLG programs are self-documenting. With the above advantages, TLG is an elegant executable metalanguage.