Philosophical Reflections on Diagram Models and Diagrammatic Representations

Diagram models are widely used in system and software engineering to design and analyse information systems. In this article, I examine diagram models within Morgan and Morrison's ‘models as mediators’ account. I argue that even though diagram models and theoretical models differ in terms of representations they deliver, namely diagrammatic and sentential representations, respectively, as theoretical models mediate between the high-level theory and the real world, diagram models mediate between the abstract system and its concrete realisation in the world. Diagram models play this mediating role through the diagrammatic representation of the dynamic and static features of the system under consideration. Moreover, I argue why diagrammatic representation proves more efficient than sentential representation as a tool of design and analysis of information systems.