Expanded bag of words representation for object classification

Currently, the bag of visual words (BOW) representation has received wide applications in object categorization. However, the BOW representation ignores the dependency relationship among visual words, which could provide informative knowledge to understand an image. In this paper, we first design a simple method to discover this dependency through computing the spatial correlation between visual words in overlapped local patches. Obtaining the dependency relationship, we further propose a novel update strategy to modify the BOW representation. The modification is motivated by the idea of Query Expansion applied successfully in text retrieval. We implement our approach on challenging PASCAL 2006 database, and the experimental results show its improved performance against the BOW representation.