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This paper describes two aspects of visualizing program systems within the object-oriented paradigm: layout specifications for graphical objects and associations of visualization and application objects. The layout approach is based on a notation similar to the TeX text formatting language. It has been extended and generalized for specifying graphical layout of user interfaces and arbitrary objects. Our simplest scheme offers specifications similar to TeX's box-and-glue metaphor. Size and position of virtual boxes and glue can be specified by simple constraints. In the second part of the paper we show how the CLOS (Common Lisp Object System) meta-level architecture can be exploited to associate visualization and application objects. We show how several useful techniques such as indirect values, slot and method demons, and instance-specific meta-objects can be implemented using CLOS. These visualizations techniques require no source code modifications of application systems. We demonstrate the feasibility of our approach using application domains such as CLOS debugging and constraint systems.

Volker Haarslev
Tue Jun 11 13:34:48 MET DST 1996