Consider a language such as Ada or Modula-2, in which a...

Consider a language such as Ada or Modula-2, in which a module $M$ can be divided into a specification (header) file and an implementation (body) file for the purpose of separate compilation (Section 10.2.1). Should $M$ 's specification itself be separately compiled, or should the compiler simply read it in the process of compiling M's body and the bodies of other modules that use abstractions defined in $M$ ? If the specification is compiled, what should the output consist of?

Key Concepts

Module Implementation

This refers to the body or the concrete code that implements the functionality declared in the module specification. It contains the executable statements and internal logic, and is typically compiled separately from the specification. The separation helps in maintaining abstraction and allows independent compilation of the implementation.

Separate Compilation

This is the process of compiling different parts of a program independently rather than as a single monolithic entity. It allows developers to compile modules separately, manage dependencies efficiently, and improve incremental compilation by only recompiling parts of the program that have changed.

Module Specification

The module specification (or interface) defines the public-facing elements of a module, such as types, procedures, and variables, without exposing the underlying implementation details. It provides the contract that other parts of the program rely on, ensuring that the module can be used correctly without needing to know its internal workings.

Compilation of Specifications

The decision on whether to compile the module specification independently or to read it during the compilation of module bodies revolves around efficiency and abstraction. Compiling the specification separately would generate a concise representation of the interface, such as a symbol table or signature, which can be used by the compiler when compiling dependent modules, ensuring consistency and reducing redundancy.

Interface Output and Abstraction Boundaries

If the specification is compiled, the expected output is an abstract description or summary of the public declarations—often in the form of a signature file or metadata—that supports type checking and linking without revealing the details of the implementation. This maintains the abstraction boundary between what is exposed to clients and the internal implementation details.

Please give Ace some feedback