Defining edges and edge weights between nodes in a network to form a graphical database. The similarity of nodes in the network is determined and an edge is defined between nodes that have a similarity measure exceeding a threshold level 805, 806. The determined similarity between the nodes defines the weight of the determined edge 807. The nodes each have an associated attribute set to which a similarity function 804 is applied in a pairwise fashion as a similarity measure between each pair of nodes. Storing similarity of nodes in this manner allows the influence of nodes to be determined and ranked to facilitate decisions such as which nodes should receive patches first or defining attack vectors. The nodes may be network nodes and the similarity may be based on attributes 801, 803 such as their features or capabilities e.g. based on a nodes UPnP XML description. Other embodiments for the nodes are also encompassed such as within citation networks, social networks, identity management and even fraud detecti
