Also list unknown files or components

[maphew]

It might be useful for the spec to list parts of the FGDB which have not been reverse engineered.

For example a00000004.horizon. This file is often (always?) present but does not serve any obvious function (meaning: deleting it seems to have no deleterious effect and they are automatically recreated whenever the f-gdb is opened by ArcGIS).

https://gis.stackexchange.com/questions/413875/what-is-function-of-horizon-files-in-file-geodatabase