1. A method comprising: generating a social network graph to model one or more social networks of related authors of online social media and their corresponding posts of online social media conversations relevant to subject matter of interest in a category, wherein generating the social network graph comprises: harvesting and aggregating posts of online social media conversations from one or more online social media sources; performing content scraping on the posts of online social media conversations to obtain raw data including each individual post of an online social media conversation relevant to the subject matter of interest and user-profile information of a social media author corresponding to each individual post; and performing social network analysis processing on the raw data to obtain the social network graph.