My Zettelkasten ID structure.
My IDs draw from an interpretation of Luhmann’s Folgezettel structure. He started with an integer for his top-level notions, as I have done. He branched from there with a separator, and typically another integer, as I’m doing, and children notions nest inward, alternating numbers and letters as each level nests further in. The separator, when used outside of the main branches from the top level, constitute a secondary branch, or an “interruption”—a link inserted after the next levels of nesting have already been taken. If a note needs to be inserted into 5123,5B7, and 5123,5B7A is already taken, it can be added as 5123,5B7,1. This is not preferable, however.