The Area Tree
Starting with the root image showing the whole mandelbrot set you can check for already calculated sub areas and zooming in using those areas.
The images are organized in a tree. The first image is labeled '0' and shows an overview of the whole set. This is the typical apple man. All other pictures are magnified sub areas of other pictures. So we finally get a hierarchy of sub areas with '0'' as the root. The names of the pictures allow to conclude the position of the pictures within the magnification hierarchy. The sub areas of a picture are labeled with lower case letters, so every picture may have up to 26 sub areas. The name 0 denotes the overview of the whole mandelbrot set, a is the name of the first sub area, b is the second sub area, etc. To compose the full name of a picture the subarea names along the path to the picture are concatenated omitting the initial 0. The name aa denotes the first sub area of the picture a, ab means the second one. Therefore acab is the second sub area of sub area a of the third sub area of the first sub area of the overview picture. For a better readability sequences of identical characters are replaced by this character with a preceeding numerical counter, e.g. the long name abaacbbb will be replaced by the short form ab2ac3b. This way every image of the database gets an unique name in the tree.