Library catalogues allow users searching of library materials in different ways. To achieve successful and efficient searching, bibliographic and authority records should be created according to cataloguing rules, besides perfect and accurate records are required. That is why, cataloguers are responsible for an adequate quality of records and the quality control should be regularly examined.
Cataloguing rules strongly inﬂuence the quality of bibliographic data, which is made obvious through the COBISS system, where data has to be transferred to the system’s data format.
With the advance of digital technology and consequently with the appearance of new media, serial publications subject has achieved previously unforeseen possibilities.
The article addresses the issue of the cataloguing rules used in Slovenia within the COBISS shared cataloguing system. The outdated cataloguing codes (PPIAK, AIK), and undocumented updates, modifications, and cataloguing practice from the last 14 years have created in the time of high-speed technological changes more and more difficulties in the development and operation of the COBISS system.