Abstract : In this paper, we describe the QASM (Question & Answer Social Media) system based on social network analysis to manage the two main resources in CQA sites: users and contents. We first present the QASM vocabulary used to formalize both the level of interest and the expertise of users on topics. Then we present our method to extract this knowledge from CQA sites. Finally we show how this knowledge is used both to find relevant experts for a question and to search for similar questions. We tested QASM on a dataset extracted from the popular CQA site StackOverflow.