Draft of ECOOP ‘ 99 Banquet Speech

In 1967 I taught at Cornell, was involved in the development of Curriculum 68, and was working on my book, Programming Languages, Information Structures, and Machine Organization, which aimed to develop a unifying model for programming languages. When Don Knuth visited me one weekend in Ithaca, we both went to the synagogue on Saturday and to Church on Sunday and had intense discussions about the nature of computer science. Don was then working on the first volume of The Art of Computer Programming and was the leading exponent of the view that computer science was the study of algorithms. Don's bottom-up approach to computer science, namely by constructing composite structures from primitives, contrasted strongly with my top-down approach of classifying and comparing already existing programming langauges. Don and I discussed the possibility of writing a joint book on data structures, but concluded that the gulf between bottom-up and top-down computer science was at this time too broad to be bridged. I first heard about Simula in 1967 and immediately fell in love with object-oriented programming, including a section on the relation between Simula '67 and Algol 60 in my 1968 book. Object-oriented programming encourages a top-down view of the world in terms of persistent objects, in contrast to algorithms that model the world bottom-up by time-independent input-output transformations. My early interest in object-oriented programming led to a close relationship with Kristen Nygaard who, like me, was a top-down researcher. At a panel discussion on the nature of inheritance at the Oslo ECOOP in 1988, Kristen asserted that inheritance models specification, while Danny Bobrow of the United States took the bottom up position that inheritance models implementation. European computer scientists frequently take a top-down view that emphasizes principles and esthetics, while American computer scientists frequently take a bottom-up view based on practical and implementation considerations. My top-down approach is based partly on my European roots and European education. My quest for top-down understanding led to a series of articles and edited books that explore research directions of computing. The 80-page 1970 article " Three Computer Cultures: Computer Mathematics, Computer Engineering, and Computer Science " considered computer science as a synthesis of the intellectual traditions of mathematics and engineering. My 1980s edited book " Research Directions in Software Engineering included a 80-page article " Research Directions in Programming Languages ". Here are some quotes from the introduction to this article: " Programming …