A VSE directory is a directory stored on a VSE host and managed by the VSE Librarian.
A VSE directory name may be up to 16 characters in length, of the form lllllll.ssssssss where lllllll is up to 7 characters in length and ssssssss is up to 8 characters in length. Both lllllll and sssssss are composed of the letters A-Z, the numerals 0-9, and the special characters dash (-), dollar sign ($), at sign (@), pound sign (#), and the underscore (_).
In VSE parlance, the lllllll is known as the VSE library and the lllllll.ssssssss (or just ssssssss) is known as the VSE sublibrary.