A NodeEnumeration is used to iterate over a list of nodes. An AxisEnumeration
is a NodeEnumeration that throws no exceptions; it also supports the ability
to find the last() position, again with no exceptions.
Determine whether there are more nodes to come.
(Note the term "Element" is used here in the sense of the standard Java Enumeration class,
it has nothing to do with XML elements).
Get the next node in sequence.
(Note the term "Element" is used here in the sense of the standard Java Enumeration class,
it has nothing to do with XML elements).