EIFFEL: Object-Oriented Design for Software Engineering

Eiffel is an object-oriented language and environment combining the advances in reusable, flexible programming brought by object-oriented techniques with the concerns introduced by modem software engineering, particularly correcmess, reliability and efficiency. As a language, Eiffel offers an extensive combination of facilities: multiple and repeated inheritance, polymorphism and dynamic binding, deferred features, export controls, generically parameterized classes, assertions and invariants expressing correcmess arguments, full static type checking. The implementation, currently available on Unix (System V and BSD), provides automatic configuration management, efficient resolution of dynamic binding (in constant time), and a set of tools for automatic documentation and debugging. It is complemented by a library of carefully designed software components. Eiffel is designed as a portable and open system. Eiffel classes may be combined with code written in other languages, and portable C packages may be produced from Eiffel text. Care has been taken, however, to preserve the integrity of the language; the interfaces between Eiffel classes and external code are strictly delimited. Eiffel is not an experimental tool but a production system which has been installed at a number of user sites in Europe, Japan and North America, both in companies and universities, and has been applied to a number of significant developments since it was made commercially available in September of 1986. Beyond the language and environment aspects, Eiffel promotes a method of software construction by combination of reusable and flexible modules. The design of Eiffel was an attempt to provide quality-conscious software developers-including ourselves, since Eiffel was an internal tool before it was made publicly available-with a environment to produce high-quality software. The software qualities factors that were particularly sought in this endeavor were correctness, reliability, reusability, extendibility and reusability. In oar opinion, the principles of object-oriented design provide the best known techniques for attaining these qualities. The definition of object-oriented design which serves as the basis for this discussion is the following: object-orientexl design is the construction of software systems as structured collections of abstract data type implementations. Eiffel classes are abstract data type implementations not only in principle, but more concretely through the use of explicit assertions (preconditions, postconditions, invariants) which reflect the axioms of the abstract data type specifications. The word structured, as used in the definition, refers to the mechanisms used for combining modules. The