Introduction

The visualization of structured information is crucial in many application domains. For example, in computer science it is used for software engineering, database design, network management, visual programming, etc.

One of the best ways to represent any kind of structured information is to model it by a graph. Graphs are mathematical objects that consist of a set of vertices, connected by a set of edges. When a graph is used to represent some data, its vertices model data elements, and its edges model dependencies between data elements. If the information is organized too complex to be modelled by a classical graph, more complex graph formalisms should be considered. An example of such formalisms is the hierarchically clustered graphs. A hierarchically clustered graph is a classical graph, vertices of which are divided into hierarchically nested fragments.

Graph models can be used in practice only along with support tools, that provide the visualization of graphs. The increasing amounts of information, people have to deal with, cause a growing need of graph drawing systems and libraries. On the other hand, modern computers have enough power to perform effective graph visualization.

For these reasons many graph drawing systems have been developed in recent years. Among such systems Higres is one of the best universal tools that work under Microsoft Windows 95 and NT.

Ivan Lisitsyn