“…Annotation itself can simply be considered to be (a) the generation of features that can be indexed for retrieval purpose, for example, through consideration of text associated with an image, (b) features directly extracted from image content, or (c) automatic annotation based on some form of contextual information associate with the image (Zhang, Islam, & Lu, ). As discussed above, the first two approaches can generate indexing features, but these features often do not match the terms used by those seeking images; in other words, they fall victim to the semantic gap (Sandhaus & Boll, ; Smeulders et al., ). In the following text, we therefore first review literature exploring how images are annotated, with the aim of identifying appropriate indexing terms.…”