Networks structure describes a set of entities and the relations between them. A social network, for example, delivers information on persons in some population and the relations between them, which may describe associations of collaboration, friendship, correspondence and so on. An information network, as extra example, may define technical publications and their reference links. In their most rudimentary form, networks are modeled by a graph, where the nodes of the graph denote to the entities, while edges denote relations between them. Factual social networks may be more composite or contain additional information.