Interaction in really graphical user interfaces

Employing diagrams in the user interface causes problems that do not exist in so-called graphical user interfaces. We are implementing a tool for generating editors for (a certain class of) diagrams from a specification. Diagram editors are needed in really graphical UIs and interactive visual language environments. This paper addresses three aspects of the specification of diagram editors. After highlighting difficulties in user interaction with diagrams event automata are suggested as a model for specification of dialogs. Furthermore, it is discussed how objects selected by the user can automatically be assembled into semantically meaningful groups. These are needed for more complex editing operations. An easy and versatile way of specifying layout for diagram editors by constraints has been introduced (Minas and Viehstaedt, 1993) and is generalized here