Abstract

The arrangement of classes in a specialization hier-archy has proved to be a useful abstraction mech-anism in class-based object oriented programming languages. The success of the mechanism is based on the high degree of code reuse that is offered, along with simple type conformance rules. The opposite of specialization is generalization. We will argue that support of generalization in addi-tion to specialization will improve class reusability. A language that only supports specialization re-quires the class hierarchy to be constructed in a top down fashion. Support for generalization will make it possible to create super-classes for already exist-ing classes, hereby enabling exclusion of methods and creation of classes that describe commonalities among already existing ones. We will show how generalization can coexist with specialization in class-based object oriented pro-gramming languages. Furthermore, we will verify that this can be achieved without changing the sim-ple conformance rules or introducing new problems with name conflicts. Permission to copy without fee all or part of this material is granted provided that the copies are not made or distributed for direct commercial advantage, the ACM copyright notice and the title of the publication and its date appear, and notice is given that copying is by permission of the Association for

Citations

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