A system for building software use cases and related state diagrams based on a model of business activities is provided. The system comprises the model of business activities and a computer based modeling tool that is used to compose the use cases and the related state diagrams. The system includes an integration component, which maps the business activities to use cases, and a graphical user interface, which illustrates the relationships among use cases and the relationships between use cases and business requirements. A state diagram component maps business activities to assist in the preparation of state activity diagrams. The model of business activities enumerates business activities and associates each business activity with the business domain in which the business activity is normally conducted. The integration component provides a list of selectable business activities to the graphical user interface from which to compose use cases and state activity diagrams.