Page "Dylan (programming language)" Paragraph 21

In Dylan, the concepts of compile-unit and import-unit are separated, and classes have nothing specifically to do with either.

A library defines items that should be compiled and handled together, while a module defines the namespace.

Classes can be placed together in modules, or cut across them, as the programmer wishes.

Often the complete definition for a class does not exist in a single module, but is spread across several that are optionally collected together.

Different programs can have different definitions of the same class, including only what they need.