Browse Books

Reviewer: James W. Moore

Most new programming languages involve novel technical features. The development of Ada also involved many unique nontechnical aspects [1]. These included a tangible statement of requirements prior to development, a design competition, a formal program of testing and evaluation at all phases of development, and extensive public comment prior to and during standardization. Furthermore, the language specifications were accompanied by a rationale document that explained the reasons for many of the language features. The rationale was originally prepared in 1978 as part of the design competition and revised the next year following the design selection. A new draft was released in January 1984 for public review following the standardization of the language and revised in 1986. (That version was widely circulated within the Ada community but apparently was never formally published.) The copyright page of the current text, dated 1991, calls it a “corrected edition.” The preface says that the goal is not to document and justify every language design decision…[but] to give the reader a feel for the spirit of the language, the motives behind the key features and to create a basis for understanding how they fit together both globally as viewed from the outside and in detail from the inside; above all to impart an appreciation of the main architectural lines of the language and its overall philosophy. The text includes an inadequate index, occupying only three pages, and a 79-entry bibliography, which in itself provides great insight into the motivations of the language designers. In general, the text is well written and pleasant to read with many relevant examples. The text shares the shortcomings of most rationale documents. It is usually descriptive, often explanatory, occasionally analytical, and rarely critical. Discarded alternatives are seldom discussed. The discussion is approached from the viewpoint of the final language rather than its requirements. It justifies the solution rather than exploring the solution space. Necessarily, the treatment is uneven and incomplete; many issues, such as the selection of the character set, are left unexplained. The poor indexing exacerbates the problem; for example, neither the contents nor the index provides any clues for finding a treatment of enumerated or character types. None of these problems detracts from the texts real value in providing insight into the thinking of the designers of the language. Some chapters, including the one on tasking, provide substantial background material on how the selected idiom relates to the literature of the time. The book is invaluable and irreplaceable for scholars and historians of the language. Users of the language are better served by a good textbook.