----------------------------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administrative unit (country, state/province) is superseded by a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
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