1. A method in a computer system for determining importance of a message of a discussion thread, the method comprising: providing messages of a discussion thread, each message having an author; identifying replied-to relationships between messages; identifying authored-by relationships between messages and authors; and calculating a value for an importance attribute of each message and a value for the expertise attribute of each author based on the replied-to and authored-by relationships, wherein the value of the importance attribute indicates the importance of a message.