The Smalltalk-80 Inspector let one browse an object structure one object at a time. We extended the Inspector with a diagram that kept a history of which objects referenced which others.
The Diagramming Inspector explores the details of object and method representation in Smalltalk-80.
Kent Beck and I built the Diagramming Inspector out of the Hot Draw framework.
We created an Object Figure with handles for each of the object's instance variables. These handles would create new objects or connect to existing object if the referenced object was already in the diagram.
The instance variable handles were much like the CreationTool in that they existed to add content to the diagram.
The Hot Draw Diagram represented the object space. It was responsible for locating the corresponding Object Figure for any object in Smalltalk-80's object space.
We described this tool and the Diagramming Debugger in our paper at the CASE '89 Conference. paper 