This application describes methods for searching digital information such as digital documents (e.g., web pages) and computer databases, and specific search techniques such as authority ranking and information retrieval (IR) relevance ranking in keyword searches. In some implementations, the technique includes analyzing digital information viewed as a labeled graph, including nodes and edges, based on a flow of authority among the nodes along the edges, the flow of authority being derived at least in part from different authority transfer rates assigned to the edges based on edge type schema information. In some implementations, the system includes an object rank module configured to generate multiple initial rankings corresponding to multiple query keywords, each of the multiple initial rankings indicating authority of nodes in a graph with respect to each respective query keyword individually; and a query module configured to combine the multiple initial rankings in response to a query.