Extracting Topic Changes through Word Co-occurrence Graphs from Japanese Subtitles of VOD Lecture

A number of universities currently utilize VOD in e-Learning systems, a form of blended learning that combines WBT (Web-Based Training) with classroom instruction. Many universities also offer e-Learning lectures, which offer slides and lecture video with VOD. However, because lectures that use standard VOD focus on letting students take the lecture, most do not include advanced search methods or implement topic detection or extraction. To aid for e-Learning users, we have been developing search facilities for VOD lectures. For this purpose, this study proposes a method of extracting the topic by creating a graph of keywords and their co-occurrence words from the lecture´s subtitles and then extracting from variations in the word the co-occurrence graphs between sentences.