ML modules provide hierarchical namespace management, as well as fine-grained control over the propagation of type information, but they do not allow modules to be broken up into separately compilable, mutually recursive components. Mixin modules facilitate recursive linking of separately compiled components, but they are not hierarchically composable and typically do not support type abstraction. We synthesize the complementary advantages of these two mechanisms in MixML. A MixML module is like an ML structure with some components specified but not defined unifing the ML structure and signature languages into one. MixML seamlessly integrates hierarchical composition, translucent MLstyle data abstraction, and mixin-style recursive linking.Tthe design of MixML is minimalist emphasizing how all the interesting features of the ML module system can be understood simply as stylized uses of a small set of orthogonal underlying constructs, with mixin composition playing a central role.
The ML Basis system extends Standard ML to support programming-in-the-very-large, namespace management at the module level, separate delivery of library sources, and more. While Standard ML modules are a sophisticated language for programming-in-the-large, it is difficult, if not impossible, to accomplish a number of routine namespace management operations when a program draws upon multiple libraries provided by different vendors. The ML Basis system is a simple, yet powerful, approach that builds upon the programmer's intuitive notion of the top-level environment (a basis). Here are some of the key features of the ML Basis system: 1. Explicit file order 2. Implicit dependencies 3.Scoping and renaming: The ML Basis system provides mechanisms for limiting the scope of (i.e, hiding) and renaming identifiers. 4.No naming convention for finding the file that defines a module. To import a module, its defining file must appear in some ML Basis file.