public String toString() {
        return displayName;
    }

    public static List<Identifier> getAll() {
        return Arrays.asList(getPunctuation(), getNonAscii(), getFileSystemReserved(), getXmlMarkup(), getWhiteSpace());
    }

    public static Identifier getPunctuation() {
        return new Identifier(PUNCTUATION_CHARS, "punctuation");
    }

    public static Identifier getNonAscii() {