In this research, the keyword extraction is viewed into a binary classification task, as shown in Figure 4. A text is given as the input, and a list of words is extracted by indexing the text. Each word is classified by the classifier into either of two labels: ‘keyword’ or ‘not’. The words which are classified into
’keyword’ are selected as the output of the keyword extraction system. For doing so, we need to collect words which are labeled with one of the two labels as sample examples, in advance.