title: difference between '/author' and 'author' in XPath query
body: <p>I am currently learning XPath query. I feel confuse When I look at these two query '/author' and 'author'. On this page <a href="http://msdn.microsoft.com/en-us/library/ms256086.aspx" rel="nofollow">http://msdn.microsoft.com/en-us/library/ms256086.aspx</a>, 'author' 
   is to find all  elements within the current context and '/author' is to find The document element () of this document. So what's the difference between them. Further, what is 'author/first-name' mean. From the example on the website above, I think it is equal to '//author/firt-name'. Do I understand it correctly?</p>