Shofiyatul Azizah, 2026. An Analysis of Inconsistencies in the Application of the Dewey Decimal Classification (DDC) System to Library Collections at the Darul Ilmi Library of MAN 2 Ponorogo. Islamic Library and Information Science Study Program, Faculty of Islamic Studies, Universitas Muhammadiyah Ponorogo. Supervisor I: Dr. Katni, M.Pd.I., Supervisor II: Ayu Wulansari, S.Kom., M.A.

Collection classification is an essential pillar of library management, as it serves as the foundation for information retrieval systems. However, preliminary observations at the Darul Ilmi Library of MAN 2 Ponorogo revealed inconsistencies in the application of the Dewey Decimal Classification (DDC) system, such as collections with similar subjects being assigned different classification numbers. This condition has the potential to disrupt the structure of the collection and hinder users’ information retrieval processes. This study aims to identify the forms of inconsistency in determining classification numbers for collections with similar titles or topics and to identify the factors contributing to such inconsistencies. This study employed a qualitative approach with a descriptive research design. Data were collected through limited participant observation, interviews, and documentation, and were analyzed using the interactive model of Miles, Huberman, and Saldaña. Data validity was ensured through source and technique triangulation. The findings revealed four forms of inconsistency: the simultaneous use of two Islamic notations (297 and 2X), the placement of Islamic collections in general classes (200/201), differences in call numbers among copies with identical titles, authors, and editions, and errors in assigning disciplinary classes to non-fiction collections. These inconsistencies were caused by six factors: differences in librarians’ experience and training, variations in reference sources, the complexity of collection subjects, limitations in facilities and infrastructure, staff fatigue during data entry, and a history of limited human resources for collection processing.

Keywords: Inconsistency, DDC Classification, Islamic Notation, Information Retrieval, School Library