In a fast-changing industry like publishing, the simple things are often the most useful. That’s why in fields like science, technology, engineering and medicine, which have long been on the leading edge of online publishing, workflows are rapidly moving toward HTML-based production—after all, HTML is the language of the web, and that’s where all the software tools are.

One such system that I have been personally involved with is the Open Publication Distribution System (OPDS). OPDS is akin to an RSS or syndication feed for publisher catalogs. It was originally developed by Lexcycle (before Lexcycle was acquired by Amazon) as a simple way of presenting e-books available for sale on the Stanza mobile e-book platform. The Lexcycle founders, who lacked a background in publishing, did not want to wrestle with Onix, a complicated metadata scheme (as publishers know) that was designed for B2B management, not for consumers.

Today, OPDS is probably the most heavily used publishing and library standard you’ve never heard of. As publishing confronts a fast-changing commercial landscape, OPDS is one of many simple, open standards that are enabling flexible online discovery, purchase, and distribution of magazines, e-books, and other media.

What is OPDS?

In its most basic form, an OPDS catalog is a list of links. Each link takes the reader to a web page about a book, with information that might include additional descriptions (such as bibliographic information and a summary), a digital transaction point where the book can be sold, or, for libraries, a way for patrons to borrow the book. While I was at the Internet Archive, I made over three million digitized public domain books available to Kobo, Barnes & Noble’s Nook, and the Asus media content platform simply by creating an OPDS catalog. Retailers are able to harvest the data in an OPDS catalog and smoothly integrate the books into their online commerce sites. And other kinds of publishers and distributors, such as Feedbooks and, use OPDS to list the books that they are making available, permitting the books to appear on third-party storefronts or book discovery portals.

Enhancements have been made to OPDS to support library transactions, including those utilizing digital rights management (DRM) systems such as Adobe Content Server (ACS). For example, the Library Simplified project, led by the New York Public Library with support from the U.S. Institute for Museum and Library Services, is building a commercial-grade e-book discovery and reading service that enables library patrons to borrow e-books seamlessly from multiple distributors using a single mobile app. Built on top of Readium, the Readium Foundation’s ePub 3 reader software, Library Simplified will ideally make it nearly as easy to borrow an e-book as it is to purchase one from an online retailer. Library Simplified uses OPDS to present the list of available books from Overdrive, 3M, and public domain sources to library patrons in exactly the same way that Lexcycle’s Stanza application did for retail.

International Reach

The appeal of OPDS is global. The developers of the French Feedbooks platform are contributing features to Readium, and drafting changes to OPDS, so that both can support a new DRM standard called Lightweight Content Protection, as OPDS can easily be enhanced to support e-book retrieval for new DRM systems, as well as other developments. For example, other extensions for the library market might include more explicit support for retrieving the circulation status of e-books, or placing holds on popular books.

And applications for OPDS are indeed rapidly expanding around the world. Prêt Numérique en Bibliothèque (PNB), the innovative French library lending system, created as a partnership of French publishers and e-book distributors, now lets libraries present e-books in an OPDS format. In fact, some of the first libraries to implement PNB, including ones in Paris and Grenoble, are considering requiring OPDS in any e-book lending platforms they use.

As the e-book ecosystem matures, it’s becoming clear that the best, most efficient way to support targeted new digital services is by utilizing and building upon good, existing standards and practices, rather than seeking new replacements. On that score, given the rapid growth in its implementations, OPDS is worthy of newfound consideration for the e-reading market.