Although diagrammatic representations have been a feature of human com- nication from early history, recent advances in printing and electronic media technologyhaveintroducedincreasinglysophisticatedvisualrepresentationsinto everydaylife. We need to improve our understanding of the role of diagramsand sketches in communication, cognition, creative thought, and problem-solving. These concerns have triggered a surge of interest in the study of diagrammatic notations, especially in academic disciplines dealing with cognition, compu- tion, and communication. We believe that the study of...