Mixins are modules in which some components are deferred , i.e. their definition has to be provided by another module. Moreover, differently from parameterized modules (like ML functors), mixin modules can be mutually dependent and their composition supports redefinition of components (overriding). In this paper, we present a formal model of mixins and their basic composition operators. These operators can be viewed as a kernel language with clean semantics in which to express more complex operators of existing modular languages, including variants of inheritance in object oriented programming. Our formal model is given in an "institution independent" way, i.e. is parameterized by the semantic framework modeling the underlying core language. Introduction In object oriented languages, the definition of an heir class H from a parent class P takes usually the form H = extend P by M , where M denotes a collection of definitions of components (typically methods) which are either new, or re...

We define a kernel language for the manipulation of mixin modules with the aim of providing foundations for the design of advanced module systems. Several working examples are presented showing the benefits of the use of mixins and overriding in module systems; moreover, a set of typing rules ensures that the language supports separate compilation. The denotational semantics of the language is based on an algebraic approach and is parametric in the semantics of the underlying core language. Hence, even though the language is defined on top of a specific core language, other kinds of core languages could be considered. Introduction In this paper we define a simple modular language supporting the notion of mixin module. The notion of mixin comes directly from object oriented programming (OOP). One of the aims of this paper is showing that this notion can be fruitfully applied to modular systems as well. According to the OO terminology, a mixin is an abstract subclass (a class where the...

. This paper shows that class inheritance, viewed as a mechanism for composing self-referential namespaces, is a broadly applicable concept. We show that several kinds of software artifacts can be modeled as self-referential namespaces, and software tools based on a model of composition of namespaces can effectively manage these artifacts. We describe four such tools: an interpreter for compositionally modular Scheme, a compositional linker for object files, a compositional interface definition language, and a compositional document processing tool. We show that these tools benefit significantly from incorporating inheritance-based reuse. Furthermore, the implementation of these tools share much in common since they are based on the same underlying model. We describe a reusable OO framework for efficiently constructing such tools. Three of the above tools were built by directly reusing the application framework, and the fourth evolved in parallel with it. We provide reuse...