At George Mason University, a project is underway to support software engineering lifecycles, methods, and prototyping environments to support software reuse at the requirements and design phases of the software lifecycle, in addition to the coding phase. A reuse-oriented software lifecycle, the Evolutionary Domain Lifecycle [Gomaa89, Gomaa91] has been proposed, which is a highly iterative lifecycle that takes an application domain perspective allowing the development of families of systems. A domain analysis and modeling method has also been developed [Gomaa90]. This paper describes the prototype software engineering environment that has been developed to demonstrate these concepts.