Read XSLT 2.0 and XPath 2.0 Programmer's Reference, 4th Edition Online
Authors: Michael Kay
\w | A character considered to form part of a word, as distinct from a separator between words: specifically a character that does not match \p{P} or \p{Z} or \p{C} |
\S | Any character that does not match \s |
\I | Any character that does not match \i |