Welcome to the Metadata Millennium: A Complete Overview of What Metadata Can Do for Publishers
To address this Tower of Babel-like problem of publishers having different types of metadata in multiple formats, standards have been developed over the years. While today most of these standards are expressed as XML, they typically predate XML by many years. And the standards tend to evolve, because the needs of publishers and everyone in the supply chain evolve. Therefore, there are standards bodies -- usually governed by or guided by a coalition of parties throughout the industry -- to establish, publish, and maintain them. Three important ones for the book supply chain are ONIX, BISAC, and Thema.
ONIX -- which stands for ONline Information eXchange -- is a standard originally released in 2000 and maintained by EDItEUR, an international organization based in London. ONIX for Books is an extremely rich collection of terms and codes (and their definitions) that enables publishers to describe, in a consistent manner that is widely understood, literally hundreds of possible pieces of information needed in the supply chain. It is a messaging format: it's not intended to make publishers throw out their databases and start over, it's just how information in those databases should be communicated to the outside world. It has become widely -- nearly universally -- adopted throughout the world. ONIX "code lists" are updated quarterly, based on input from publishing organizations around the world (BISG, the Book Industry Study Group, provides the input from the U.S.).
But there's a catch. Remember I said that standards need to evolve? Well this is a big one. Over time it was realized that the monolithic architecture of the ONIX standard (as expressed in XML) had become an impediment to future development and effective use. A new model called ONIX 3.0 was released in 2009 that is much more capable of expressing what publishers today need to express, and that can be maintained more effectively over time. ONIX 3.0 is more modular than ONIX 2.1, contributing in part to it not being fully backwards compatible with 2.1.