string concat(string, string, string*) The concat function returns the concatenation of its arguments. boolean starts-with(string, string) The starts-with function returns true if the first argument string starts with the second argument string, and otherwise returns false. boolean contains(string, string) The contains function returns true if the first argument string contains the second argument string, and otherwise returns false. string substring-before(string, string) The substring-before function returns the substring of the first argument string that precedes the first occurrence of the second argument string in the first argument string, or the empty string if the first argument string does not contain the second argument string. For example, substring-before("1999/04/01","/") returns 1999. string substring-after(string, string) The substring-after function returns the substring of the first argument string that follows the first occurrence of the second argument string in the first argument string, or the empty string if the first argument string does not contain the second argument string. For example, substring-after("1999/04/01","/") returns 04/01, and substring-after("1999/04/01","19") returns 99/04/01.