Preußische Instruktionen
The Preußische Instruktionen (abbreviated PI, German for 'Prussian Instructions') were a set of cataloging rules used in scientific libraries in German-speaking countries and, to some extent, abroad. First published in 1899, the PI were replaced by other sets of rules such as the Regeln für die alphabetische Katalogisierung (RAK) from the 1980s onwards, which in turn have been replaced by the Resource Description and Access (RDA) rules since 2015.