Result diversification in image retrieval based on semantic distance

User requirements for result diversification in image retrieval have been increasing with the explosion of image resources. Result diversification requires that image retrieval systems are made capable of handling semantic gaps between image visual features and semantic concepts, and providing both relevant and diversified image results. Context information, such as captions, descriptions, and tags, provides opportunities for image retrieval systems to improve their result diversification. This study explores a mechanism for improving result diversification using the semantic distance of image social tags. We design and compare nine strategies that combine three different semantic distance algorithms (WordNet, Google Distance, and Explicit Semantic Analysis) with three re-ranking algorithms (MMR, xQuAD, and Score Difference) for result diversification. In order to better prove the effectiveness of our strategy of applying semantic information, we also make use of visual features of images for result diversification experiment and make comparison. Our data for experimentation were extracted from 269,648 images selected from the NUS-WIDE datasets with manually annotated subtopics. Experimental results affirm the effectiveness of applying semantic information for improving result diversification in image retrieval. In particular, WordNet-based semantic distance combined with the Score Difference (WordNet-DivScore) outperformed other strategies in diversifying image retrieval results.