A method and system for ranking importance of vertices of a directed graph based on links between the vertices and some prior knowledge of importance of the vertices is provided. A ranking system inputs an indication of the vertices along with an indication of the links between the vertices as the directed graph. The ranking system generates a transition-probability matrix that represents the probability of transitioning from vertex to vertex. The ranking system then generates a ranking of the vertices based on the links between the vertices represented by the stationary distribution of the transition-probability matrix that is minimally perturbed to satisfy the prior knowledge, which may be a partial ranking of the vertices.