string-length(string)
substring(string , numstart , numchars)
substring-before(string , substring)
substring-after(string , substring)
translate(string, fromchars , tochars)

string-length

The number of characters in the string is returned

substring

Counting from 1, the substring of length numchars starting at position numstart is returned

substring-before

The substring before the specified substring is returned

substring-after

The substring after the specified substring is returned

translate

Characters appearing in the fromchars parameter are replaced by the corresponding character in the tochars parameter otherwise the character is copied. If no character in tochars for the fromchars it is omitted