A method and system for ranking messages of discussion threads based on relationships between messages and authors is provided. The ranking system defines an equation for attributes of a message and an author. The equations define the attribute values and are based on relationships between the attribute and the attributes associated with the same type of object, and different types of objects. The ranking system iteratively calculates the attribute values for the objects using the equations until the attribute values converge on a solution. The ranking system then ranks the messages based on attribute values.