Introduction Features Audience Organisation Tracks Differences Background Information

Background and motivations

My own interest in object-oriented languages and software development stems from my research on the language DLP, a language integrating logic programming with object-oriented features and parallelism (Eliëns, 1992). When looking for material for a course on object-oriented programming, I could not find a book that paid sufficient attention to foundational and formal aspects. Most of the books were written from a perspective on OOP that did not quite suit my purposes. What I was looking for could to some extent only be found in research papers. As a consequence, I organized my OOP course around a small number of papers, selecting the papers that, to my mind, can be considered as landmark papers, papers that have become known as originally presenting some significant notion or insight. The apparent disadvantage of basing a course on OOP on papers is the obvious lack of a unified view, and of a consistent use of terminology. The advantage of such an approach, however, is that students are encouraged to assess the contribution of each paper and to form their own view by comparing critically the different viewpoints expressed in the papers. Personally, I favor the use of original papers, since these somehow show more clearly how the ideas put forward originated. Later, more polished, renderings of these same ideas often lack this quality of `discovery'.

The idea of organizing a book around slides came quite naturally, as the result of structuring the growing collection of slides, and the wish to maintain the compact representation offered by the slides.

The choice of material reflects my personal preference for foundational issues, in other words, papers that are focused on concepts rather than (mal)practice. The choice of material has also been colored by my interest in (distributed) hypermedia systems, the Web and, to some extent, by my previous work on distributed logic programming. Although the book is certainly not focused on language constructs, modeling issues as well as foundational issues are generally related to existing or conceivable language constructs, and (whenever possible) illustrated by working examples developed for that purpose.

The choice for Java as the main vehicle for presenting the program fragments and examples is motivated simply by the popularity of Java. The presentation of some of the other examples in C++ reflects my belief that C++ must still be considered as a valid programming language for object-oriented software development. However, I also believe that in the (near) future multi-paradigm approaches (extending Java and C++) will play a significant role.

The approach taken in this book may be characterized as abstract, in the sense that attention is paid primarily to concepts rather than particular details of a solution or implementation language. By chance, in response to a discussion in my class, I looked up the meaning of abstract in a dictionary, where to my surprise I learned that one of its meanings is to steal, to take away dishonestly. Jokingly, I remarked that this meaning sheds a different light on the notion of abstract data types, but at a deeper level I recognized the extent to which the ideas presented in this book have profited from the ideas originally developed by others. My rendering of these ideas in a more abstract form is, however, not meant to appropriate them in a dishonest way, but rather to give these ideas the credit they deserve by fitting them in a context, a framework encompassing both theoretical and pragmatical aspects of object-oriented computing. As one of the meanings of the adjective abstract, the dictionary also lists the word abstruse (not easy to understand). There is no need to say that, within the limits of my capabilities, I have tried to avoid becoming abstruse.

Finally, in presenting the material, I have tried to retain a sufficient degree of objectivity. Nevertheless, whenever personal judgments have slipped in, they are meant rather to provoke a discussion than provide a final answer.