DOIOriginally pitched as a kind of super-indexing tool, the Digital Object Identifier, a digital identification system that can permanently identify specific digital information and track its exchange, has grown to embrace bibliographic, rights and permissions capabilities in addition to its use as a commercial marketing, sales and content management application. The International DOI Foundation ( has certified three firms to provide DOI registration and technical support to publishers looking to implement it.

At the recent Frankfurt Book Fair, the three firms offered demonstrations of how publishers can use the DOI to control, display and exploit their content commercially. The firms are CrossRef (, a nonprofit consortium of academic publishers that helps scholarly publishers use the DOI; Content Directions, a for-profit firm that focuses on commercial applications for the DOI; and Enpia Systems, the first official DOI registration agency in Asia.

Commercial applications of the DOI were highlighted at the most recent Book Expo convention in Chicago, and the demonstrations at the Frankfurt Book Fair were meant to expand on the functionality unveiled there. Norman Paskin, director of the International DOI Foundation, said the demonstrations in Chicago "showed how a publisher can facilitate the sale of digital intellectual property while enabling the management and protection of copyright."

The DOI is a persistent digital identifier permanently attached to content. When a consumer or researcher clicks on the DOI tag, a menu of options appears, which can include whatever the publisher wants: bibliographic data, book reviews, author info, supplementary material, copyright restrictions, sales or marketing information, retail sites and much more. Paskin said that the DOI offers "proven commercial implementations that can be applied to text, images, audio and audiovisual content."

Founded by CEO David Sidman, who has been instrumental in the working groups that developed the DOI, Content Directions ( is the first firm focused on commercial applications for the DOI to be certified by the IDF, said Tina Aridas, deputy manager, marketing and press relations, for Content Directions. Aridas told PW that "commercial possibilities are beginning to drive interest in the DOI," and emphasized that while the DOI is useful for "all sorts of online content, we're really focusing on electronic books right now." Content Directions is also managing DOI-EB, an IDF project (in collaboration with McGraw-Hill, Random House, John Wiley & Sons, Microsoft, Adobe and others) that showcases the commercial viability of the DOI to the book industry.

Aridas told PW that Content Directions registered its first book DOI in late September, for The Post-Traumatic Stress Disorder Sourcebook by Glenn R. Schiraldi (McGraw-Hill), which is also being offered as a free e-book. Clicking on the book's DOI hyperlink allows the reader to buy a print edition, points to free excerpts, book reviews and much more information.

E-book publishers, print publishers (the DOI can provide the same online info for traditional books) and digital rights management firms, said Aridas, see the DOI as "just what they need; another piece in the puzzle" of selling e-books. She said the DOI offers "a unique content ID that works with every operating system; it's a global phone number that never changes. Like a supermarket barcode, it has the potential to revolutionize the sale of content."