Drawing and marking graph diagrams

The marking of graph diagrams (that is to say diagrams that are composed of nodes, possibly joined by edges) is tedious if the diagrams are presented on paper. If the key content of the diagrams is available in electronic form then the marking can be much more efficient. This is achieved because the tutor only has to mark each different diagram element once and this mark is transmitted to all diagrams that contain the element. This benefit to the tutor is obtained by requiring the students to use a diagram drawing program of some kind. However using such an editor can simplify the process for the students by allowing them to concentrate more on the problem and less on its graphical representation. The students can also be rewarded for going to this extra effort by receiving a much more detailed, personalised commentary on their work than would have been possible before, given the same amount of tutor time. We present the evolution of a drag-and-drop diagram editor specialised for the area of ER diagrams and an associated marking system with a simple but effective feedback mechanism. Some results from initial trials are presented along with some ideas for improvement and extension.