P. Doreian, A. Mrvar: Partitioning signed networks (1154. sredin seminar)

Povzetek:
Structural balance theory has proven useful for delineating the blockmodel structure of signed social networks. We relax this specification to consider actors who have positive ties to pairs of actors who belong to two mutually hostile subgroups and can act as mediators. Formalizing this idea leads to the relaxed structural balance blockmodels as a proper generalization of structural balance blockmodels. Some formal properties concerning the relation between these two models are presented along with the properties of the fitting method proposed for the new blockmodel type. The new method is applied to some empirical data where improved fits and interpretations are obtained. We extend the idea of partitioning to signed two-mode data and provide a formalization of the extension. We provide a motivating example and then use the new blockmodel type to delineate the voting patterns for the Supreme Court justices with all of their non-unanimous decisions for the 2006-7 term. Interpretations are presented together with a statement of further problems meriting attention for partitioning signed two-mode data. Finally, we provide some ideas how to partition one-mode networks by treating them two-mode data and the explicit inclusion of null blocks in blockmodel specifications for signed networks.