substring($source as xs:string?, $starting-at as xs:double) xs:string?
Returns the portion of the value of $source beginning at the position indicated by the value of $starting-at and continuing to the end of $source. The characters returned do not extend beyond the end of $source. If $starting-at is zero or negative, only those characters in positions greater than zero are returned.If the value of $source is the empty sequence, the zero-length string is returned.
substring($source as xs:string?, $starting-at as xs:double, $length as xs:double) xs:string?
Returns the portion of the value of $source beginning at the position indicated by the value of $starting-at and continuing for the number of characters indicated by the value of $length. The characters returned do not extend beyond the end of $source. If $starting-at is zero or negative, only those characters in positions greater than zero are returned. If the value of $source is the empty sequence, the zero-length string is returned.
