XPath defines twelve axes along which an XPointer may search for nodes
These depend on context to determine exactly what they point to.
For instance, consider this location path:
It begins with the
id() function that returns a
node set containing the element with the ID type attribute whose
p6. This provides a context node for the
following location step along the relative
Other axes include
Each selects nodes from a
particular subset of the nodes in the document. For instance,
following axis selects from nodes that come
after the context node. The
preceding axis selects
from nodes that come before the context node.