XML in a Nutshell, 3rd Edition

Compound Location Paths

The XPath expressions you’ve seen so far—element names, @ plus an attribute name, /, comment( ), text( ), and processing-instruction( )—are all single location steps. You can combine these with the forward slash to move around the hierarchy from the matched node to other nodes. Furthermore, you can use a period to refer to the context node, a double period to refer to the parent node, and a double forward slash to refer to descendants of the context node. With the exception of //, these are all similar to Unix shell syntax for navigating a hierarchical filesystem.