Indicizzazione semantica in SBN. Questioni, problemi, nuove sfide.

The article focuses on subject indexing in the National Library Service (Servizio Bibliotecario Nazionale -- SBN), specifically analyzing the historical premises and the diachronic developments that marked its evolution. In particular, it traces the origin and growth of the archive of subjects and classes in the SBN Index (and the collective SBN catalogue) from the founding years of the SBN cooperative bibliographic network up to the most recent transformations coming from the "Evolution of the SBN Index" project. This paper also takes into consideration the observations of the ICCU-BNCF joint working group which worked on the application of the Nuovo soggettario in SBN from 2009 up to 2010 and analyzes the project for implementation of the archive of subjects and classes of the SBN Index (2016-2017). Some considerations are proposed concerning the subject links to the Work record, thus suggesting the apical grouping by subject, which is also based on the new conceptual model IFLA Library Reference Model (LRM). [ABSTRACT FROM AUTHOR]