DAISY—Structure Guidelines: Intro to Structured Markup, The DAISY Digital Talking Book

DAISY—Structure Guidelines: Intro to Structured Markup, The DAISY Digital Talking Book


The Structure of a DAISY DTB

The DAISY DTB is a collection of digital files that provides an accessible representation of a printed book for individuals who are blind, visually-impaired, or print-disabled. These files may contain digital audio recordings of human or synthetic speech, marked up text, and a range of machine-readable files.

The structure of the book is designated by the XML tags and is accessible to the reader by use of a browser or a playback device. The DAISY DTB utilizes the technology of the Internet with the addition of some specialized applications to provide greatly improved access to the information.

There are three basic types of DAISY DTBs:

  • Audio with NCX: DTB with structure. The NCX is the Navigation Control Center, a file containing all points in the book to which the user may navigate. The XML textual content file, if present, contains the structure of the book and may contain links to features such as narrated footnotes, etc. Some DTBs of this type may also contain additional textual components, for example an index, glossary or supporting keyword searching.
  • Audio and Full Text: DTB with structure and complete text and audio. This form of a DTB is the most complete and provides the richest, multimedia reading experience and the greatest level of access for the reader. The XML textual content file contains the structure and the full text of the book. The audio and the text are synchronized.
  • Text and No Audio: DTB without audio. The XML textual content file contains the structure and full text of the book. There are no audio files. This type of DAISY DTB may, for example, be rendered with synthetic speech or with a refreshable braille display.

XML provides the producer the ability to structure a book in great detail. Compared to HTML markup, XML increases markup options and makes more detailed structure and proper nesting possible.

A DTB produced to the DAISY Standard consists of some or all of the following files:

  • A package file—a file containing administrative information about the DTB, the files that comprise it, and how these files interrelate.
  • A textual content file—containing some or all of the text of the book with appropriate markup.
  • Audio files—containing the human voice recording and/or synthetic speech rendering of the book.
  • SMIL (Synchronized Multimedia Integration Language) file(s)—containing information linking the audio and textual content files.
  • NCX—a file containing all points in the book to which the user may navigate.


The XML Document Type Definition (DTD) used for the textual content files of DAISY DTBs is the DTBook DTD. It is a machine-readable list of allowable tags, the attributes that may be applied to them, and rules on where the tags may be used.

For example, sentence tags (<sent>) can be used inside paragraph tags (<p>), but not the other way around.

To verify that a document has been marked up in accordance with a DTD, a program called a validating parser compares the markup with the DTD and lists any errors that may be present in tags, attributes, etc.

Access the current version of the DTD. Note: as DTDs are machine-readable, it requires considerable knowledge of DTDs for a human to be able to intelligently interpret the information within the file.


The NCX (Navigation Control File for XML Applications) is a critical component of the user interface of the book in that it provides a view of all the points in a text to which a user may navigate. Each navigation point in the NCX is linked through the SMIL file to the corresponding location in the audio and XML textual content files, providing direct access to that location. The NCX may not be identical to the table of contents (TOC) of the printed edition. (It will usually contain more elements of the book than the TOC does.) For DTBs containing an XML textual content file the NCX is generated from the XML markup. The way in which the markup is applied will determine what is contained within the NCX.