Does a DOI name include a check digit?
A check digit is not compulsory or necessary, but may be included. Identifiers such as URL and URI specifications, deriving from an Internet environment, do not have check digits: the underlying TCP/IP protocol they use has an error-correction component. Identifiers such as ISBN and similar bibliographic or documentation identifiers do have check digits: these act as aids to readability or keyboard data entry in the absence of any automated protocol correction.
