The software design of EUROCAT 2000, an air traffic control (ATC) system, and the integration of its components are described. Groeneveld describes how EUROCAT 2000 uses Ada plus suitable software engineering principles for the design of large modular, extensible, and maintainable ATC systems. The author intends to communicate a new system design methodology, one that constantly takes into account how system components are integrated into a working system.

We learn that modularity in the EUROCAT 2000 implementation is achieved by using off-the-shelf products with clearly defined interfaces. Overall, plenty of good software engineering goals and design principles are mentioned, such as the use of standard components, languages, and protocols; adherence to modularity; and strict interface specification.

We learn that component integration is done in a controlled, step-by-step way using the SPMS+ software project management system. We learn about its two layers. The first layer, for development and experimentation, is the “system level software component” level. Usable modules ready for integration are then copied to the reference area in the second layer, the “system level.” Finally, the paper concludes with the list of references.

On the positive side, the use of off-the-shelf products perfectly coincides with the goals of Ada. If EUROCAT did in fact accomplish this component reuse goal, the return of investment is great and the paper thus provides a excellent proof of concept of correct language design for Ada.

The part on SPMS+ is an interesting, high-level introduction to a tool used in EUROCAT 2000, and that part of the paper could serve as a top-level, online manual for implementors.

The negatives or, more accurately, the missing parts outweigh the positive. Initially the reader gets the impression that the paper describes how continual integration of new system components into an already working system is achieved while the partial system is operational. This integration is a great system implementation goal and truly a difficult task. Later it becomes clear that the reader’s impression was wrong; nothing is integrated into a working system while it runs.

The paper fails to show how and where off-the-shelf modules were used for EUROCAT; it would have been important to convey how to do this. It is an elusive goal of many system houses, and readers love to learn about this. I was full of hope when I saw this allusion and frustrated when I observed that the necessary detail is missing.

The paper explains that modular design, the separation of public interfaces from private implementation detail, and the use of standards are good design and implementation principles. The paper also states that all these are used in EUROCAT 2000. Likely, the reader already knew these good principles. The reader wants to find out how the principles were satisfied in EUROCAT 2000, yet the paper is silent about that. Hence it is disappointing and comes across as somewhat hollow. Concluding with a list of references is simply failure to admit that a conclusion is missing.

I do not know who should read this much too brief paper. I was curious when I saw the title. I wish I had learned more about ATCs. The main information I could glean from the paper was hidden in Figure 1, which shows parallel activities of ATCs with aircraft and with pilots in real time. How this parallel activity, actually multiple instantiations of this, can be implemented modularly in an extensible way was supposed to be described, according to the abstract and introduction. Yet the author did not keep that wonderful promise.

Perhaps the paper will be useful to a fellow implementor, an insider of EUROCAT 2000 who has all sources of the Ada system available. For an outsider, the presentation is unsatisfactory, however. Overall, the publication is too wordy for the amount of information conveyed and too short for the complex subject and the announced goals. The listed design principles leave little doubt that the author succeeded in mastering a complex task, but he has failed to tell how he did this. He must have had wonderful experiences, which remain hidden. Readers curious about the subject should use the author’s phone number, given in the paper, and thus acquire the significant information. It must be somewhere, but it is not communicated.