For request reference properties, the presence of this key,
only if its value is AttributeConstants.TRUE, states that
this notification will be the last one to be published
for the current batch of requests.
When found at the end of an attribute key name or request reference
property, this constant signifies
that the value of the attribute is the number of elements in the
attribute group of the text before this key.
If a LogProxy's attribute key name or request reference property
begins with the value of this constant, the attribute is related
to the description of log entries.