The Unified process is yet another method of Agile Development.  One of the key strengths of this process is that it encourages its users to tweak and change it so that it meets their needs.  Activities and artifacts in this process are considered optional and can be done or not as the team decides.  Even the order in which steps are done are up to the project team.   As a result there are a number of different variatons on this including the Agile Unified Process, the Rational Unified Process,