Abstract
The National Diet Library collects and maintains a database (Collaborative Reference Database) of reference service questions and the answers given to them. The questions are submitted to public and university libraries by users, and the answers are given by the libraries. This project support reference service and research activities. In Collaborative Reference Database, Property of “Nippon Decimal Classification (NDC) codes” is optional, and the NDC codes are assigned to only about 2/3 records because such codes can be burdensome to reference librarians. This paper proposes a method for automatically assigning Nippon Decimal Classification (NDC) codes to them using machine learning. NDC codes allow users to easily find reference service records and are therefore useful. We propose following two methods. (1) Using the NDC codes of the reference materials in reference recodes, (2) using frequency of each NDC of morpheme in question in reference recodes, and (3) using both method. For our experiments, we used 62,328 reference records. Experimental result showed that our method achieved a 45.6% precision about (1). And our method achieved a 53.8% precision about (2). And our method achieved a 45.6% precision about (3). These figures are significantly higher than 32.4% precision of the preceding studies.
