This is an intermediate level between AST and CIVL-IR (model).

• tree representation of a program, like AST
• whole program represented by one tree (no notion of "translation unit", etc.)
• every variable is declared in one and only one place
• no prototypes --- you can call a function even before it is declared or defined
• no side-effects. assignments are statements. function calls are statements.
• some simplification of types?

This is a good level on which to perform transformations.