Online Information Exchange (ONIX) is a universal, internationally used metadata format for books. The ONIX format allows book publishers and editors to distribute electronic information about books on the Web to wholesalers and bookstores or to other publishers. The ONIX specifications were developed by the Association of American Publishers, Book Industry Communication
and the Book Industry Study Group. Metadataplays
an important role in book sales because it is used for book descriptions in bookstores, book brochures, and online bookstores. Therefore, most publishers and sales chains use the standardized ONIX format, which defines the metadata used to describe the book's title and author, content, physical book format, ISBN number, selling price, or book reviews, among other things. In addition, the ONIX standard specifies the format in which the ONIX data is transmitted. The format is flexible in terms of the amount of text in the individual data fields and offers the possibility of adding multimedia elements such as the title display or audio files. Each data element is tagged as if with XML tags and is thus compliant with Document Type Definition (DTD).