The majority of new acquisitions of the Bayerische Staatsbibliothek since 2001 has already undergone classificatory subject indexing with notations of the so-called BSB-DDC, which are short notations of the Dewey decimal classification system for the aspects of subject, geography and time. The number of systematically indexed titles now amounts to 1.5 million. Since the beginning of April 2020, classification search has been possible in the OPACplus as well for the subject fields of classical studies, studies of history, musicology and eastern and south-eastern Europe.
The high-quality subject indexing, which had been used predominantly for the recent acquisitions services so far, can thus also be used for thematic searches for research literature of the past two decades. This constitutes a substantial enhancement of subject-related search possibilities. While a search with subject headings searches for "narrow" terms in a targeted way, classificatory search makes possible researching wider thematic fields. The option of combining subject terms with geographical regions and temporal epochs can allow for searches which are impossible to accomplish by a search with subject headings (for instance with respect to the lack of search possibilities for time keywords) or can be accomplished only with great effort.
The access point "Classification search (sub-collections)" can be found in the OPACplus by opening the menu item "Search" and selecting the third entry next to "Basic search" and "Advanced search".