Diagram interpretation and e-learning systems

We describe a system capable of grading free-form diagrammatic answers. Our system matches meaningful parts of a diagram with equivalents in a model solution. This is complicated by errors, omissions, and superfluous items in the student answer. The result of matcing is used to calculate the grade and generate appropritae feedback; it performs at least as well as a human marker on a variety of diagram types. We describe tools that allow the easy creation of questions, marking schemees, and diagram editors suitalbe for embedding in a VLE quiz engine