----------------------------Original message---------------------------- David, Nice to meet you in so many meta-places! In our library we work with an area classification specifically designed by the CCK (Dutch Union Map Catalogue). If a administrative unit (country, state/province) is superseded by a new administrative unit which is larger than the former, then the old unit becomes a keyword linked to the code of the new unit. If the new unit is smaller, the old unit keeps its existing code. E.g. <4.410> Bundesrepublik Deutschland [1945-1990] <4.420> Deutsche Demokratische Republik [1949-1990] becomes <4.415> Bundesrepublik Deutschland [1990- ] <4.415> Bundesrepublik Deutschland [1990- ] : Bundesrepublik Deutschland [1945-1990] <4.415> Bundesrepublik Deutschland [1990- ] : Deutsche Demokratische Republik [1949-1990] and <4.440> Ceskoslovensko [ -1992] becomes <4.435> Ceskezeme [1993- ] <4.440> Ceskoslovensko [ -1992] <4.445> Slovensko [1993- ] However when we describe an old map we try to give it an area-denomination which is consistent with the era it depicts. So your old East-German maps get the thesaurus-number of <4.420> Deutsche Demokratische Republik [1949-1990] BUT when output is created (on screen or in hard-copy) the output-programme links through automatically and the presentation will be: <4.415> Bundesrepublik Deutschland [1990- ] : Deutsche Demokratische Republik [1949-1990]. There is a restrictiction. The classification is based on the administrative division of the world as it existed in 1980. Administrative units not in existence then anymore became keywords on existing codes. As we have 999 possibilities for country-codes per continent, and 999 possibilities for subdivisions per countries we think we can stand a few centuries of political changes. Hopes this information helps you somewhat. Jan Smits Mapcurator Royal Library, the National Library of The Netherlands [log in to unmask]