As a major practical example, we present an editor for UML class diagrams. We show that direct-manipulation editing capabilities can enhance the usability of such an editor in comparison to standard tools. A further improvement is obtained by including selective abstraction features similar to the well-known "fisheye-viewing" and "semantic zooming" paradigms. We show that the proposed generator architecture provides an excellent base for implementing such features. The resulting technique can be applied to a wide range of different diagram languages; in contrast to other general solutions, it takes into account the abstract structure and specific abstraction features of the individual languages.
In this paper, we use the terms "visual language" and "diagram language" as synonyms.
J. Clark and S. DeRose. XML path language (XPath). W3C recommendation 16 November 1999, W3C, 1999. http://www.w3.org/TR/xpath.
Object Management Group. Unified Modelling Langugage Specification. http://www.omg.org/uml/.