## 2 Background  
Understanding the structure and characteristics of the UDC system is essential for evaluating automated classification approaches and interpreting our experimental results. This section outlines the key features of the UDC system that are particularly relevant to large language model-based classification, including its hierarchical organization, faceted structure, and multilingual capabilities. UDC is a comprehensive, faceted classification system designed to organize and categorize knowledge across all fields of information. Developed by [PERSON] and [PERSON] in 1895, UDC is based on [PERSON]'s Decimal Classification but significantly expands upon it with faceted classification, auxiliary tables, and combination capabilities. The system uses a combination of numbers and symbols to create a hierarchical structure that can represent complex subjects and their interrelationships (Tables 1 and 2). One of the key strengths of UDC is its flexibility and extensibility. It employs a faceted approach, allowing for the combination of multiple concepts to describe a document's content precisely. This is achieved through the use of auxiliary signs and special auxiliaries, which enable the expression of various aspects such as time, place, form, and language. For example, the notation \"621.39:681.3\", where the colon (:) indicates a relationship between the two concepts, represents \"telecommunication in relation to computer science,\" demonstrating the system's ability to express complex interdisciplinary subjects. UDC offers several advantages for information organization. Its hierarchical structure facilitates both broad and narrow searches, making it equally useful for general browsing and specific information retrieval. The system's language-independent nature, relying on numbers and symbols, makes it particularly valuable in multilingual or international contexts. Moreover, UDC's logical structure and combinatorial capabilities make it well suited for computer-based applications and digital library systems. These characteristics make UDC particularly suitable for automated classification approaches, as the hierarchical structure enables similarity measures that can assess partial correctness at different hierarchical levels (Table 3). \begin{table}
\begin{tabular}{c l} \hline \hline
**Notation** & **Description** \\ \hline \multirow{3}{*}{0} & Science and Knowledge, Organization, Computer Science, \\  & Information Science, Documentation, Librarianship, \\  & Institutions, Publications \\ \hline \multirow{3}{*}{1} & Philosophy, Psychology \\ \hline \multirow{3}{*}{2} & Religion, Theology \\ \cline{1-1}  & Social Sciences \\ \cline{1-1}  & \(4\) \\ \cline{1-1}  & _vacant_ \\ \cline{1-1}  & 5 \\ \cline{1-1}  & Mathematics, Natural Sciences \\ \cline{1-1}  & 6 \\ \cline{1-1}  & Applied Sciences, Medicine, Technology \\ \cline{1-1}  & 7 \\ \cline{1-1}  & The Arts, Entertainment, Sport \\ \cline{1-1}  & 8 \\ \hline \multirow{3}{*}{9} & Geography, History \\ \hline \hline \end{tabular}
\end{table} 
Table 1: The top-level classes of the main tables in the UDC. \begin{table}
\begin{tabular}{c l} \hline \hline
**Notation** & **Description** \\ \hline \multirow{3}{*}{0} & Science and Knowledge, Organization, Computer Science, \\  & Information Science, Documentation, Librarianship, \\  & Institutions, Publications \\ \hline \multirow{3}{*}{00} & Prolegomena, Fundamentals of knowledge and culture, \\  & Propaedeutics \\ \hline \multirow{3}{*}{004} & Computer science and technology, Computing, Data processing \\ \cline{1-1}  & 004.7 \\ \cline{1-1}  & Networks according to area covered \\ \hline \multirow{3}{*}{004.738} & Network interconnection, Internetworking \\ \cline{1-1}  & 004.738.5 \\ \cline{1-1}  & Internet \\ \cline{1-1}  & 004.738.52 \\ \hline \end{tabular}
\end{table} 
Table 2: Hierarchical breakdown of the UDC code 004.738.52. However, UDC is not without its challenges.