AspectJ-TM is a simple and practical aspect-oriented extension to Java-TM. With just a few new constructs, AspectJ provides support for modular implementation of a range of crosscutting concerns. In AspectJ's dynamic join point model, join points are well-defined points in the execution of the program

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Abstract. Mixin layers are a technique for implementing layered object-oriented subclasses (mixin classes) but scaled to a multiple-class granularity. We describe mixin layers from a programming language viewpoint, discuss checking the consistency of a mixin layer composition, and analyze the language support issues involved. 1

A "refinement" is a functionality addition to a software project that can affect multiple dispersed implementation entities (functions, classes, etc.). In this paper, we examine large-scale refinements in terms of a fundamental object-oriented technique called collaboration-based design. We explain how collaborations can be expressed in existing programming languages or be supported with new language constructs (which we have implemented as extensions to the Java language). We present a specific expression of large-scale refinements called mixin layers, and demonstrate how it overcomes the scalability difficulties that plagued prior work. We also show how we used mixin layers as the primary implementation technique for building an extensible Java compiler, JTS.

Generic programming centers around the idea of abstracting from concrete, efficient algorithms to obtain generic algorithms that can be combined with different data representations to produce a wide variety of useful software. For example, a class of generic sorting algorithms can be defined which work with finite sequences but which can be instantiated in different ways to produce algorithms working on arrays or linked lists. Four kinds of abstraction---data, algorithmic, structural, and representational--- are discussed, with examples of their use in building an Ada library of software components. The main topic discussed is generic algorithms and an approach to their formal specification and verification, with illustration in terms of a partitioning algorithm such as is used in the quicksort algorithm. It is argued that generically programmed software component libraries offer important advantages for achieving software productivity and reliability. This paper was presented at the...

We develop an imperative calculus that provides a formal model for both single and mixin inheritance. By introducing classes and mixins as the basic object-oriented constructs in a -calculus with records and references, we obtain a system with an intuitive operational semantics. New

An overview of the software design and data abstraction decisions chosen for deal.II, a general purpose finite element library written in C++, is given. The library uses advanced object-oriented and data encapsulation techniques to break finite element implementations into smaller blocks that can be arranged to fit users requirements. Through this approach, deal.II supports a large number of different applications covering a wide range of scientific areas, programming methodologies, and application-specific algorithms, without imposing a rigid framework into which they have to fit. A judicious use of programming techniques allows to avoid the computational costs frequently associated with abstract object-oriented class libraries. The paper presents a detailed description of the abstractions chosen for defining geometric information of meshes and the handling of degrees of freedom associated with finite element spaces, as well as of linear algebra, input/output capabilities and of interfaces to other software, such as visualization tools. Finally, some results obtained with applications built atop deal.II are shown to demonstrate the powerful capabilities of this toolbox.

Combinations of C++ features, like inheritance, templates, and class nesting, allow for the expression of powerful component patterns. In particular, research has demonstrated that, using C++ mixin classes, one can express layered component-based designs concisely with efficient implementations. In this paper, we discuss pragmatic issues related to component-based programming using C++ mixins. We explain surprising interactions of C++ features and policies that sometimes complicate mixin implementations, while other times enable additional functionality without extra effort.

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.

The promises of object-orientation and distributed computing could be delivered if the software we needed were written in stone. But it isn't, it changes. The challenge of distributed object-oriented maintenance is to find a means of evolving software, which already has a distributed client base.