Smart Diagram Environments (SDEs) are software applications that use structured diagrams to provide a natural visual interface. Such an environment behaves as if the computer “understands” the diagram, for example by providing manipulation that takes into account the diagram’s structure and its intended semantics. We present Cider. Cider is a generic component-based system which is designed to be easily embedded in Java applications. It provides automatic interpretation of diagrams as they are constructed and manipulated, structure preserving manipulation, and a powerful transformation system for specifying diagram manipulations. Cider’s main innovation is its component-based approach to SDE development which provides substantially increased architectural flexibility to the application programmer.