Locally Adaptive Density Ratio for Detecting Novelty in Twitter Streams

With the massive growth of social data, a huge attention has been given to the task of detecting key topics in the Twitter stream. In this paper, we propose the use of novelty detection techniques for identifying both emerging and evolving topics in new tweets. In specific, we propose a locally adaptive approach for density-ratio estimation in which the density ratio between new and reference data is used to capture evolving novelties, and at the same time a locally adaptive kernel is employed into the density-ratio objective function to capture emerging novelties based on the local neighborhood structure. In order to address the challenges associated with short text, we adopt an efficient approach for calculating semantic kernels with the proposed densityratio method. A comparison to different methods shows the superiority of the proposed algorithm.