The definitions file contains lines of the form
symbol := value
where symbol is an identifier, following normal Ada (case-insensitive) rules for its syntax, and value is one of the following:
Empty, corresponding to a null substitution
A string literal using normal Ada syntax
Any sequence of characters from the set (letters, digits, period, underline)
Comment lines may also appear in the definitions file, starting with the usual -, and comments may be added to the definitions lines.