Visualising the structure of object-oriented systems

Executing object-oriented programs have a complex structure consisting of numerous objects connected by interobject references. This structure, called the program´s object graph, is hard to understand, and this complicates learning, teaching, debugging and maintaining object-oriented programs. While visualisation can be used to display object graphs, the size and complexity of typical object graphs also makes visualisation difficult. We have developed ownership trees as a simple yet powerful method of extracting a program´s implicit encapsulation structure from its object graph. We present a program visualisation tool that makes use of ownership trees to display the structure of object-oriented programs. Our prototype implementation suggests that visualisations based on ownership trees can effectively display the structure of fifty to sixty objects in a program simultaneously