Definition
signature_def : signature identifier { decl_list }
Purpose
A signature_def defines a signature. The signature's name is identifier. The body of the signature is given by decl_body. A signature by itself will not generate any program structures. Signatures are used to describe modules.
Semantics
The signature may contain only declarations which are empty. It may not define or initialize any elements.
Exactly one sugnature_def may coexist with exactly one uninitialized sugnature_decl of the same name.
