Sustainability of Digital Formats: Planning for Library of Congress Collections

The NISO Digital Talking Book Standard, ANSI/NISO Z39.86-2002, defines the format and content of the electronic file set that comprises a digital talking book (DTB) and establishes a limited set of requirements for DTB playback devices. It uses established and new specifications to delineate the structure of DTBs whose content can range from XML text only, to text with corresponding spoken audio, to audio with little or no text. DTBs are designed to make print material accessible and navigable for blind or otherwise print-disabled persons.

The standard comprises a set of files, including a mandatory package file, which incorporates a manifest listing all the other component files and a spine, which indicates logical reading order. Component files can be of several types, including: textual content (in XML); audio files; image files; synchronization files (in SMIL); navigation control files (in XML); bookmark/highlight files (in XML).

The National Library Service for the Blind and Physically Handicapped (NLS) is using DTB_2002_NLS, the extended version of the standard for the production of NLS talking books. As of April 2009, none of the NLS talking books include full text and there are no plans to produce books with full text.

Bookshare.Org, which provides full-text books to print-handicapped users, makes the full text (without audio) of books available in several formats, including the NISO DTB standard (aka DAISY 3).

A forty-member panel representing educators, publishers, technology specialists, and advocacy groups, sponsored by Office of Special Education Programs at the U. S. Department of Education recommended, in a report released in July 2004, that a specific application (or profile) of the NISO DTB standard be adopted as version 1 of the National Instructional Materials Accessibility Standard (NIMAS). The National Center on Accessible Instructional Materials provides a list of hardware and software supporting DTB and DAISY specifications.

• Audio with Title element only: DTB without structure. This is the simplest class of DTB and is used for books where structure will not be applied. The XML textual content file may not be present, or if it is, contains only the title of the book, and other required notation. The book must be read linearly. Direct access to points within the DTB is not possible.
• Audio with NCX only (Navigation Control): DTB with structure. The XML textual content file, if present, contains only the structure of the book and may contain links to features such as narrated footnotes, etc. This is the most common form of DTB and is ideal for stand-alone players.
• Audio with NCX and partial text: DTB with structure and some additional text. The XML textual content file contains only the structure of the book and the text of components where keyword searching and direct access to the text would be beneficial, e.g., index, glossary, etc.
• Audio and full text: DTB with structure and complete text and audio. This form of a DTB is the most complex but provides the greatest level of access. The XML textual content file contains the structure and the full text of the book. The audio and the text are synchronized.
• Full text and some audio: DTB with structure, complete text and limited audio. The XML textual content file contains the structure and the text of the book. The audio files contain recordings of parts of the text. This type of DTB could be used for a dictionary where only pronunciations were provided in audio form.
• Text and no audio: E-text with structure. The XML textual content file contains the structure and text of the book. There are no audio files.