Motivated by Googles great success on text document retrieval, researchers began to build a new generation of video retrieval systems supporting semantic video retrieval via keywords. But these systems are unable to provide satisfactory results because of several challenging problems. First, existing semantic understanding techniques are still immature, and their performance is not good enough to enable keyword-based retrieval. Second, the mismatch between visual concepts and keywords prevents any keyword-based search engines from retrieving visual concepts that are difficult to represent in...