Network analysis is an important step in the understanding of complex systems studied in various areas such as biology, geography or sociology. This thesis focuses on the problems related to the decomposition of those networks when they are modeled by graphs. Graph decomposition methods are useful for data compression, community detection or network visualisation. One possible decomposition is a hierarchical partition of the set of vertices. We propose a method to evaluate the quality of such structures using quality measures and algorithms to maximise those measures. We also discuss the design of effective visual metaphors to represent various graph decompositions.
