AbstractThis paper presents a diagrammatic logic framework that is suitable for use in formal specification and for reasoning about and refining formal software models. We take a case study style approach to presenting the framework by developing, in some detail, an abstract model for a transparent configuration control platform. The model is built up by stages, corresponding to separate concerns of configuration control. Each successive level is a refinement of the previous level. We discuss the possibilities for developing tools to support the use of the diagrammatic logic, including automated diagram drawing and reasoning procedures. Our wider goal is to make a formal specification easier for its clients to understand