A homogeneous system structure is proposed that enhances modularity and flexibility, and facilitates (further) development of large-scale software systems in a major-industry environment. In our opinion, it is an effective means of countering the inherent increase in software entropy when (further) developing existing large-scale software systems, thereby substantially cutting down production costs. It can be applied generally both to new and existing systems, whether application programs or operating systems, promotes the parallel use of different programming paradigms and various implementation languages, and offers the option of either redesigning parts or introducing additional parts in stages based on a more modern technology. The proposed system structure is compared and contrasted with other architectures such as CORBA, and it is shown that it may be regarded as an embellishment of the CORBA architecture for the internal structuring or restructuring of possibly distributed software systems. So far it has been used in four releases of the BS2000/OSD operating system with very positive results. Dependencies between various entities – which we call ‘subsystems’ – in the course of the (further) development process, as well as during dynamic execution are minimized and well-regulated. The subsystems may be loaded on demand during the session by a system authority. Every interface in the system is classified according to its permitted scope of use. For interfaces between subsystems, a uniform and standardized technique is introduced which uses the same format for all implementation languages at both the source- and binary-code level. This technique exceeds the regulations in other architectures but actually achieves considerable rationalization. Copyright © 1999 John Wiley & Sons, Ltd.

The paper investigates the applicability of the object-oriented technique to large and complex systems as exemplified by the operating system BS2000 which has been under constant development for a number of years. The proposed system architecture ensures the harmonious coexistence of procedural and object-oriented parts of the system. New domains, which are implemented using the object-oriented paradigm, can be smoothly embedded in the existing system. The parallel usage of different implementation languages is rendered economically viable. In our framework some representative parts of the system were redesigned and implemented in a prototype. The extensibility of the design was checked by including further parts into this scheme. The results are encouraging, so that the object-oriented technique will be used in the further development process. The proposed technique can also be applied to systems with a different structure, even a monolithic one.>