We designed and implemented a prototype software development environment based on software component composition. Our software development environment, the Entity-Relationship Software Development Environment (ERSDE), uses extended entity-relationship diagrams (EERDs) as templates of executable programs.An EERD represents the component types and the relationship types among them within an application domain. The graphical editor of the ERSDE uses an EERD as a menu in constructing application software.An EERD used as a menu can enforce legitimate patterns of relationships among software components, in addition to providing an intuitive view of available components and possible relationships among them.Furthermore, as the ERSDE uses structural active objects as the components of a program, we can obtain an executable program if those components are instantiated and interconnected as dictated by an EERD. Two experiments conducted confirmed the effectiveness of our approach.