A method, system, and computer program product for exercising rights based on determining trust in an issuance of a rights expression, including issuing rights expressions by a chain of servers, forming a chain of rights expressions issued from server to server and finally from the last server to a client,...http://www.google.com/patents/US20040220878?utm_source=gb-gplus-sharePatent US20040220878 - Networked services licensing system and method
