DIANA (Descriptive Intermediate Attributed Notation for Ada) is an intermediate language used to represent the semantics of an Ada program.
It was originally designed as an interface between the compiler front end (syntactic analysis) and middle end (semantic analysis) of the compiler on the one hand and the compiler back end (code generation and optimization) on the other.
DIANA is an abstract data type; its concrete implementations are defined using the IDL specification language.
DIANA descends from TCOL and AIDA, earlier representations of Ada programs.
The full Karlsruhe Ada compilation system used DIANA as well and the IDL External Representation for marshalling between the middle-end and the code generating back-end.