Complex sentence: The Unified Process is not simply a process, but rather an extensible framework which should be customized for specific organizations or pzzzzzzzzzzzzzzzzzzz whether a refinement of the process was derived from UP or from RUP, and so the names tend to be used interchangeably.
Split into simpler sentences: The Unified Process is not simply a process, but rather an extensible framework which should be customized for specific organizations or projects. As a result it is often impossible to say whether a refinement of the process was derived from UP or from RUP, and so the names tend to be used interchangeably.