The category scheme for maps initiated in 2006 hinged on removing the ambiguous description "historical" from map category names. "Historical maps of the world", for example, may mean old maps of the world, or modern maps showing world history, or old maps showing even older world history...
The basis for the scheme, therefore, is relatively straightforward:
1. Maps in a name means modern maps, i.e. maps made in the past seventy (70) years.
2. Old maps in a name means maps over seventy (70) years ago.a
3. Every "Maps..." category may have an "Old maps..." category as its first subcategory.b
4. Category:Maps showing history therefore contains modern maps that show history.
Its subcategories are mostly Maps of the history of....
5. Category:Old maps showing history therefore contains "old maps" (as defined above) showing even older history.
Its subcategories are mostly Old maps of the history of...
For every subcategory of Category:Maps, there may be a similar subcategory of Category:Old maps. Or, more technically, Category:Maps and Category:Old maps are parallel, complementary networks of categories.