Extended Backus-Naur Form (EBNF) [ISO/IEC-14977] is a notation used for expressing context-free grammars, describing all possible legal statements that match an expression. The syntax used to describe the encoding and decoding of an NCRenameDescription tuple to and from a string is a modified version of EBNF, hereafter called Extended Backus-Naur Form--Modified (EBNF-M). EBNF-M is defined here and is used to express an instance (or set of equivalent instances) of a legal statement based on an instance of a tuple. The elements defined in the following sections have been added to EBNF to produce EBNF-M.