Online Extra: How the "Digital Object Identifier" Works

The book industry and the record industry are deeply intertwined. The retail sale of recordings is based on the methods of book publishing, and many bookstores derive much of their revenue from the sale of recordings. Some of the book industry's giants, such as AOL Time Warner and Germany's Bertelsmann, are also huge players in recorded music.

On one critical issue, however, what are in some ways two branches of the same industry have taken dramatically different courses. Faced with the opportunities and challenges of digital distribution, the music industry has chosen to fight the new technology at every turn. While the lawsuit that has effectively shut down Napster's music-sharing service was the most visible part of the campaign, the record companies have opposed even paid downloads of music until an ironclad system of preventing unauthorized copying is in place.