String Concat (String, String, String *) join two strings
Boolean Starts-with (String, String) Judging whether a string starts with another string
Boolean Contains (String, String) Judging whether a string contains another string
String Substring (String, Number, Number) Subsidence
Number string-length (string) measure string length
Number SUM (Node-Set)
Number Floor (Number) is less than the maximum integer value of this number
Number CEILING (NUMBER) is greater than this minimum integer value
