substring function returns a part of a given string.
substring(string, start) substring(string, start, length)
The string to evaluate.
The position within*
string* the substring begins
The length of the substring. If omitted, the returned string will contain every character from the
startposition to the end of
As in other XPath functions, the position is not zero-based. The first character in the string has a position of 1, not 0.