+An I<Identifier> is of the form
+C<I<host>B</>I<plugin>B<->I<instance>B</>I<type>B<->I<instance>> with both
+I<instance>-parts being optional. If they're omitted the hyphen must be
+omitted, too.
+
+A I<Value-List> is a colon-separated list of values, prepended by the time
+stamp in epoch, i.E<nbsp>e. the same format RRDTool uses, see L<rrdupdate(1)>.
+As with the argument passed to RRDTool you can use B<N> as the current time and
+B<U> for undefined values. However, undefined values can only passed for
+B<GAUGE> values. When setting B<U> for a B<COUNTER> data source the behavior is
+undefined.
+
+Since examples usually let one understand a lot better, here are some: