Context-exploiting shapes for diagram transformation

DIAGEN [1] is a tool for generating diagram editors that respect the syntax of partic-ular diagram languages. Editors generated with DIAGEN work as follows: A drawing tool allows free-hand editing of diagrams, by arranging diagram primi-tives like boxes, circles, lines, text on a drawing pane. The set of available primitives depends on the particular diagram language. A scanner analyses the spatial relationships of diagram primitives, and reduces them to diagram symbols like states and transitions. Finally, a parser checks whether the diagram symbols are related according to the syntax of the diagram language, and produces a derivation structure. DIAGEN relies on hypergraphs and hypergraph transformation: diagrams are rep-resented as hypergraphs, the scanner is specified by hypergraph transformation rules, and the syntax of diagram languages is specified by hypergraph grammars. (See [5] for details.) Case studies with editors for control flow diagrams, Nassi-Shneiderman diagrams, message sequence charts, state charts, and UML class diagrams indicate that the syntax of practically every kind of diagram language—also for design language