declare name-letters string string

A declaration used to identify an uppercase/lowercase relationship of characters above ASCII 127.

There are several constraints on this declaration:

• The two strings that are the arguments of the name-letters declaration must be of the same length
• The characters in the first string must be between "%128" and "%255".
• Characters can't be duplicated in the first string.
• Characters in the second string must be valid name characters: English letters, digits, ".","-","_" or "%128" to %255.
• No characters in the second string may have an English lowercase equivalent in the first string.

This means that:

• Every name character must be either lowercase or uppercase, but never both. A name character is lowercase if it is an English lowercase letter or if it appears in the first string in the declare name-letters declaration. A name character is uppercase if it is not lowercase.
• Every lowercase name character has a unique corresponding uppercase name character that is a different character than its lowercase version.
• Every uppercase English letter, digit, ".", "-", "_", the characters from the range "%128#" to "%225#" in the second argument, and the characters from the range "%128#" to "%225#" in neither the first or second argument, are all uppercase letters.

In the final analysis, an uppercase name character has zero, one, or more than one lowercase name character.

• There is no requirement to have a corresponding lowercase name character. This is typically for non-alphabetic characters: the digits and ".", "-", "_". Though, if these are specified, there may be lowercase values for these characters.
• An uppercase name character can have a single corresponding lowercase equivalent. This is typically the case in English letters, though again, it may be explicitly altered.
• An uppercase name character may have more than one lowercase equivalent. This typically occurs in languages with more forms of a lowercase version, usually by means of accents than by the uppercase name character.. French and Spanish are good examples of this.

Versions of OmniMark prior to V3 permitted only English letters to be used as letters in names. Digits, "-" and "." were also permitted, as long as they did not start the name. V3 extends the set of letters permitted in unquoted names to include all of the characters in the ACII character set with a value greater than 127. This allows accented European letters (for example) to be used in unquoted names. OmniMark V3 allows the underscore ("_") in names, provided it is not the first character.