Operations for evolving specifications

We have been studying a model of software specification reuse which begins with the retrieval of relevant specification components, and then successively adapts and composes these components to construct a desired complete specification. The focus of the paper is on the composition of reusable specification components. We use semantically-based composition operations-that is, operations that are designed to guarantee certain semantic properties of the composite artifact if certain properties hold of the input artifacts-to build complex specifications and to design new reusable specification components reactively. We describe the implementation of four composition operations, and illustrate their use by means of a small scenario