Nagy et al. addresses the scalability issues for visual vocabulary based image annotation algorithms as new object categories are added. To this end, a hierarchical approach is proposed based on classspecific vocabulary and a scoring function. Fan et al. reported an extensive analysis of user behavior in online video streaming based on a large-scale trace database of online video access sessions. The study of the statistical characteristics of user behavior patterns shows that user behavior in a video access session is not only related to the content of the video, but also has strong correlation with the behaviors of previous access sessions. Wang and Merialdo propose an approach to boost the performance of video concept detection based on the Bag-of-Words through the assignment different weights to the visual words according to their informativeness for the detection of different concepts.
