This paper describes a prototype domain modeling environment used to demonstrate the concepts of reuse of software requirements and software architectures. The environment, which is application-domain independent, is used to support the development of domain models and to generate target system specifications from them. The prototype environment consists of an integrated set of commercial-off-the-shelf software tools and custom developed software tools. The concept of reuse is prevalent at several levels of the domain modeling method and prototype environment. The environment is domain-independent thereby supporting the specification of diverse application domain models. The domain modeling method specifies a family of systems rather than a single system; optional features characterize the variations in functional requirements supported by the family, and individual family members are specified by the features they are to support. The knowledge-based approach to target system generation provides the rules for generating target system specifications from the domain model; target system specifications, themselves, may be stored in an object repository for subsequent retrieval and reuse.< >