People who write object-oriented programs concentrate on implementing useful classes. There is a tremendous motivation to capture and catalog classes so that they can be accessed by large segments of the programming community. Many substantial class libraries exist and others are being developed worldwide. Software is increasingly being constructed from existing, well-defined, carefully tested, well-documented, portable, high-performance, widely available components. This kind of software reusability speeds the development of powerful, high-quality software. Rapid applications development (RAD) through the mechanisms of reusable componentry has become an important field.
Significant problems must be solved, however, before the full potential of software reusability can be realized. We need cataloging schemes, licensing schemes, protection mechanisms to ensure that master copies of classes are not corrupted, description schemes so that designers of new systems can easily determine whether existing objects meet their needs, browsing mechanisms to determine what classes are available and how closely they meet software developer requirements and the like. Many interesting research and development problems need to be solved. There is great motivation to solve these problems, because the potential value of their solutions is enormous.