In the following chapter, background and related work are discussed. Relationship-based clustering and visualization is presented in chapter 3 [SG00c,SG00a,SG00b,SG01,GS02,SG02b]. In chapter 4 [SGM00] we present a comparison over a variety of clustering approaches in document clustering with a novel evaluation framework. In chapter 5 [SG02a], we introduce the cluster ensemble problem and several methods to solve it heuristically. Chapter 6 concludes the dissertation with a summary of the contributions to cluster analysis and presents some future directions of research.