| The complexity of software has driven both researchers and practitioners toward design methodologies that decompose problems into intellectually manageable pieces and that assemble partial products into complete software artifacts. Modularity in design, however, rarely translates into modularity at the implementation level. Hence, an important problem is to provide implementation (i.e., programming language) support for expressing modular designs concisely.; This dissertation shows that software can be conveniently modularized using large-scale object-oriented software components. Such large-scale components encapsulate multiple classes but can themselves be viewed as classes, as they support the object-oriented mechanisms of encapsulation and inheritance. This conceptual approach has several concrete applications. First, existing language mechanisms, like a pattern of inheritance, class nesting, and parameterization, can be used to simulate large-scale components called mixin layers . Mixin layers are ideal for implementing certain forms of object-oriented designs and result in simpler and more concise implementations than those possible with previous methodologies. Second, we propose new language constructs to provide better support for component-based programming. These constructs express components cleanly (i.e., without unwanted interactions with other language mechanisms) and address the issue of component type-checking. |
