A Structural Analysis of topic ontologies

DMOZ is the largest human-edited topic ontology available on the Web. This article studies the structural properties of the DMOZ graph. A number of global and local properties of this graph and the subgraphs resulting from isolating edges of different types are examined by means of metrics commonly used in complex network analysis. In particular, we investigate the presence of various features that characterize small-world networks. This analysis is complemented by examining other characteristics of the graphs such as connectivity and centrality measures. The connectivity and centrality patterns are further studied by means of visualizations of the graphs' k-core decomposition and a selection of strongly connected components. Several non-trivial regularities that are also encountered in other artificial and natural complex networks provide a general picture of this large human-edited topic ontology. This analysis is of major pragmatic interest as it allows a better understanding of notions such as navigability among topics, hierarchical structure and topic cohesiveness, which are of great importance in the design of topic ontologies.