The design of an intermediate representation is critical to compiler portability and code generation efficieucy.In order to increase the reusability of compiler components

and to simplify the development process of compilers

the paper presents an abstract intermediate representation (AIR) that provides a concise notation for describing the abstract syntax of programming language

and the inner data structures of compilers. AIR integrates algebraic data types into the object-oriented paradigm and thus makes it have stronger expressive power

flexibility

and extensibility. AIR separates the abstract descriptions from the concrete implementation. This makes it easier to be implemented in different high-level languages and thus improves the interoperatibility of compiler components. We use AIR to simulate the core of the SUIF written in C++. The result states that AIR has stronger expressive power and more compact syntax than the other languages for describing the abstract syntax of programming languages.