A system for controlling the distribution and use of digital works using digital tickets. In the present invention, a "digital ticket" is used to entitle the ticket holder to exercise some usage right with respect to a digital work. Usage rights are used to define how a digital work may be used or distributed....http://www.google.com/patents/US20030023561?utm_source=gb-gplus-sharePatent US20030023561 - System for controlling the distribution and use of digital works
