Abstract: According to the characteristics of online social network and the shortcomings of the existing community detection algorithms, this paper proposed an improved community detection algorithm based on semantic technology ISLPA (Improved Semantic Label Propagation Algorithm). ISLPA is suitable for discovering and identifying community structure in the larg}scale online social network. It is an improved SemTagP algorithm, combining with semantic and social tagging technology. hhis algorithm takes advantage of the semantic information and topology features of online social network to community structure discovering. ISLPA doesn't rectuire a priori information such as the number and size of communities while it's used to discovery community structures in largcscale online network,and it can also automatically identify the detected communities according to the tagging labels. This algorithm is much efficiency because it takes nearly linear time complexity. The experiment shows that SLAP algorithm can effectively discover and identify community structure for real online social networks.

Key words: Community detection, Label Propagation, Semantic Web, Social tagging