This master's thesis examines the possibilities of correction and change in a classification scheme, with regard to the changes that occur in the world the classification system intends to describe. Applying a comparative method and classification theory, the classification of the example of the former Yugoslavia (1918-1941, 1945-1991), its republics and successor states, and the languages, formerly known as Serbo-Croatian are examined through a comparison of the main classes and divisions of language, geography, and history, in Dewey Decimal Classification (DDC), and Klassifikationssystem för svenska bibliotek [Classification for Swedish Libraries] (SAB). Eight editions of DDC, from 1876 to 2014, are compared to seven editions of SAB, from 1921 to 2013. The editions have been selected in order to show the changes prior to, and following, the First World War, changes after the Second World War, and changes following the collapse of Yugoslavia in 1991. The examination shows that both systems have updated their editions according to the changes in former Yugoslavia over the years. DDC has well constructed facet schedules, especially Table 2 concerning geography, but fails, in some cases, to construct a logic and hierarchical structure for the republics and languages of Yugoslavia, partly due to the fixed classes and divisions that survive from the very first edition of DDC from 1876, but also as a result of the decimal notation, and its limitations, itself. SAB seeks to construct a hierarchically logic and equal scheme for the languages, areas, and states of the former Yugoslavia. Although the facets for geography and chronology aren't as developed as the ones in DDC, the overall result is that of a logically consistent and hierarchically clear classification, with short notation codes, thanks to the alphabetic mixed notation, which allows more subdivisions than the numerals and the pure notation of DDC. This study is a two years master's thesis in Archive, Library and Museum studies.