Abstract: This standard 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.
An American National Standard Developed by the National Information Standards Organization
Approved April 21, 2005 by the American National Standards Institute
Published by
NISO Press
4733 Bethesda Avenue, Suite 300
Bethesda, MD 20814
www.niso.org
Copyright ©2005 by the National Information Standards Organization.
All rights reserved under international and Pan-American Copyright Conventions. For noncommercial purposes only this publication may be reproduced or transmitted in any form or by any means without prior permission in writing from the publisher. All inquiries regarding commercial reproduction or distribution should be addressed to NISO Press, 4733 Bethesda Avenue, Suite 300, Bethesda, MD 20814 USA.
ISSN: 1041-5653 National Information Standards Series
ISBN: 1-880124-63-7
(This preface is not a part of ANSI/ Z39.86-2005, Specifications for the Digital Talking Book. It is included for information only.)
ANSI/NISO Z39.86 was first released in 2002. Preparation of this version of the standard was prompted by several factors: first, a desire to stay abreast of current practices in related standards and specifications; second, a need to clarify a few ambiguities present in the first release; and third, the wish to add enhancements requested by those using, or planning to use, the standard.
A variety of changes stemming from all of the above reasons were made. Some of the more significant enhancements are listed below:
Individual changes made to the standard are described in comments that can be viewed by reading the HTML version in an HTML authoring tool or with a text editor.
(This foreword is not a part of ANSI/ Z39.86-2005, Specifications for the Digital Talking Book. It is included for information only.)
This standard presents specifications for digital talking books (DTBs) for blind, visually impaired, physically handicapped, learning-disabled, or otherwise print-disabled readers. For many years, "talking books" have been made available to print-disabled readers on analog media such as phonograph records and audiocassettes. These media serve their users well in providing human-speech recordings of a wide array of print material in increasingly robust and cost-effective formats. However, analog media are limited in several respects when compared to a print book. First, they are by their nature linear presentations, which leave much to be desired when reading reference works, textbooks, magazines, and other materials that are often accessed randomly. In contrast, digital media offer readers the ability to move around in a book or magazine as freely as (and more efficiently than) a sighted reader flips through a print book. Second, analog recordings do not allow users to interact with the book by placing bookmarks or highlighting material. A DTB offers this capability, storing the bookmarks and highlights separate from, but associated with, the DTB itself. Third, talking book users have long complained that they do not have access to the spelling of the words they hear. As will be explained below, some DTBs will include a file containing the full text of the work, synchronized with the audio presentation, thereby allowing readers to locate specific words and hear them spelled. Finally, analog audio offers readers only one version of the document. If, for example, a book contains footnotes, they are either read where referenced, which burdens the casual reader with unwanted interruptions, or grouped at a location out of the flow of the text, making them difficult for interested readers to access. A DTB allows the user to easily skip over or read footnotes. The Digital Talking Book offers the print-disabled user a significantly enhanced reading experience -- one that is much closer to that of the sighted reader using a print book.
The DTB goes far beyond the limits imposed on analog audio books because it can include not just the audio rendition of the work, but the full textual content and images as well. Because the textual content file is synchronized with the audio file, a DTB offers multiple sensory inputs to readers, a great benefit to, for example, learning-disabled readers. Some visually impaired readers may choose to listen to most of the book, but find that inspecting the images provides information not available in the narrative flow. Others may opt to skip the audio presentation altogether and instead view the text file via screen-enlarging software. Braille readers may prefer to read some or all of the document via a refreshable Braille display device connected to their DTB player and accessing the textual content file. DTBs containing a textual content file but no audio material might be accessed via synthetic speech, screen-enlarging software, or a Braille device.
Digital Talking Books are not tied to a single distribution medium. CD-ROMs will be used first but DTBs will be portable to any digital distribution medium capable of handling the large files associated with digital audio recordings. Regardless of how a DTB is distributed, however, it will normally be in the context of an intellectual property protection system.
Suggestions for improving this standard are welcome. They should be sent to the National Information Standards Organization, 4733 Bethesda Avenue, Suite 300, Bethesda, MD 20814 USA, telephone (301) 654‑2512.
This Standard was processed and approved for submittal to ANSI by the National Information Standards Organization. NISO approval of this Standard does not necessarily imply that all Voting Members voted for its approval. At the time it approved this Standard, NISO had the following members:
3M
Susan
Boettcher
Roger
D. Larson, Alt
American
Association of Law Libraries
Robert
L. Oakley
Mary
Alice Baish, Alt
American
Chemical Society
Matthew
Toussant
American
Library Association
Betty
Landesman
American
Society for Information Science and Technology (ASIS&T)
Gail
Thornburg
American
Society of Indexers
Judith
Gibbs
American
Theological Library Association
Myron
Chace
ARMA
International
Diane
Carlisle
Armed
Forces Medical Library
Diane
Zehnpfennig
Emily
Court, Alt
Art
Libraries Society of North America (ARLIS/NA)
Mark
Bresnan
Association
for Information and Image Management (AIIM)
Betsy
A. Fanning
Association
of Information and Dissemination Centers (ASIDIC)
Margie
Hlava
Association
of Jewish Libraries
Caroline
R. Miller
Elizabeth
Vernon, Alt
Association
of Research Libraries
Duane
E. Webster
Julia
Blixrud, Alt
Auto-Graphics,
Inc.
Paul
Cope
Barnes
& Noble, Inc.
Douglas
Cheney
Book
Industry Communication
Brian
Green
California
Digital Library
Daniel
Greenstein
John
Kunze, Alt
Cambridge
Information Group
Michael
Cairns
Matthew
Dunie, Alt
College
Center for Library Automation (CCLA)
Richard
Madaus
Ann
Armbrister, Alt
Colorado
State Library
Brenda
Bailey-Hainer
Steve
Wrede, Alt
CrossRef
Edward
Pentz
Amy
Brand, Alt
Davandy,
L.L.C.
Michael
J. Mellinger
DYNIX
Corporation
Ed
Riding
Gail
Wanner, Alt
EBSCO
Information Services
Gary
Coker
Oliver
Pesch, Alt
Elsevier
Paul
Mostert
Endeavor
Information Systems, Inc.
Sara
Randall
Shelley
Hostetler, Alt
Entopia,
Inc.
Igor
Perisic
Ex
Libris, Inc
James
Steenbergen
Fretwell-Downing
Informatics
Robin
Murray
Gale
Group
Katherine
Gruber
Justine
Carson, Alt
Geac
Library Solutions
Eric
Conderaerts
Eloise
Sullivan, Alt
GIS
Information Systems, Inc.
Candy
Zemon
Paul
Huf, Alt
H.W.
Wilson Company
Ann
Case
Patricia
Kuhr, Alt
Helsinki
University Library
Juha
Hakala
Index
Data
Sebastian
Hammer
David
Dorman, Alt
INFLIBNET
Centre
T A
V Murthy
Rajesh
Chandrakar, Alt
Infotrieve
Jan
Peterson
Innovative
Interfaces, Inc.
Gerald
M. Kline
Betsy
Graham, Alt
International
DOI Foundation, The
Norman
Paskin
Ithaka/JSTOR/ARTstor
David
Yakimischak
Bruce
Heterick, Alt
John
Wiley & Sons, Inc.
Eric
Swanson
Library
Binding Institute
Debra
Nolan
Library
Corporation, The
Mark
Wilson
Ted
Koppel, Alt
Library
of Congress
Sally
H. McCallum, Alt
Los
Alamos National Laboratory
Richard
E. Luce
Lucent
Technologies
M.E.
Brennan
Medical
Library Association
Nadine
P. Ellero
Carla
J. Funk, Alt
MINITEX
Cecelia
Boone
William
DeJohn, Alt
Modern
Language Association
Daniel
Bokser
B.
Chen, Alt
MuseGlobal,
Inc.
Kate
Noerr
Clifford
Hammond, Alt
Music
Library Association
Mark
McKnight
David
Sommerfield, Alt
National
Agricultural Library
Eleanor
G. Frierson
Gary
K. McCone, Alt
National
Archives and Records Administration
Nancy
Allard
National
Library of Medicine
Betsy
L. Humphreys
National
Security Agency
Kathleen
Dolan
NFAIS
Marjorie
Hlava
Nylink
Mary-Alice
Lynch
Jane
Neale, Alt
OCLC
Online Computer Library Center
Thomas
Hickey
Openly
Informatics, Inc.
Eric
Hellman
ProQuest
Information and Learning
Thomas
Hamilton
Carol
Brent, Alt
Random
House, Inc.
Laurie
Stark
Recording
Industry Association of America
Bruce
Block
Carlos
Garza, Alt
RLG
Lennie
Stovel
Joan
Aliprand, Alt
Sage
Publications
Carol
Richman
Richard
Fidczuk, Alt
Serials
Solutions, Inc.
Mike
McCracken
SIRSI
Corporation
Greg
Hathorn
Slavko
Manojlovich, Alt
Society
for Technical Communication (STC)
Frederick
O'Hara
Annette
D. Reilly, Alt
Society
of American Archivists
Lisa
Weber
Special
Libraries Association (SLA)
Foster
J. Zhang
Synapse
Corporation
Trish
Yancey
Dave
Clarke, Alt
TAGSYS,
Inc.
John
Jordon
Anne
Salado, Alt
Talis
Information Ltd
Terry
Willan
Katie
Anstock, Alt
The
Cherry Hill Company
Cary
Gordon
Thomson
ISI
Carolyn
Finn
Triangle
Research Libraries Network
Mona
C. Couts, Alt
U.S.
Department of Commerce, NIST, Office of Information Services
Mary-Deirdre
Coraggio
U.S.
Department of Defense, DTIC (Defense Technical Information Center)
Richard
Evans
Jane
L. Cohen, Alt
U.S.
DOE, Office of Scientific & Technical Information
Ralph
Scott
Karen
Spence, Alt
U.S.
Government Printing Office
Judith
Russell
T.C.
Evans, Alt
U.S.
National Commission on Libraries and Information Science (NCLIS)
Robert
Molyneux
VTLS,
Inc.
Carl
Grant, Alt
WebFeat
Todd
Miller
Paul
Duncan, Alt
At the time NISO approved this standard, the following individuals served on its Board of Directors:
Jan Peterson, Chair
Infotrieve
Carl Grant, Vice Chair/Chair-Elect
VTLS, Inc.
Beverly C. Lynch, Immediate Past
Chair
UCLA Graduate School of Education & Information
Studies
Michael J. Mellinger, Treasurer
Davandy, L.L.C.
Patricia R. Harris, Executive
Director/Secretary
National Information Standards Organization
Douglas Cheney
Barnes & Noble, Inc.
Brian Green
BIC/EDItEUR
Daniel Greenstein
California Digital Library
Deborah Loeding
The H.W. Wilson Company
Richard E. Luce
Los Alamos National Laboratory
Robin Murray
Fretwell- Downing Informatics
James Neal
Columbia University
Oliver Pesch
EBSCO Information Services
Patricia Stevens (SDC Chair)
OCLC, Inc.
Eric Swanson
John Wiley & Sons, Inc.
Following approval of this standard in 2002, an advisory committee was formed to oversee the maintenance and enhancement of the document. The following individuals comprised the committee during the preparation of this version of the standard.
The Advisory Committee gratefully acknowledges the substantial contributions made by the following individuals to the continuing development of the standard. In particular, Ole Holst Andersen gave greatly of his time and expertise to the effort. The DAISY Consortium's XML-Techniques working group also provided excellent feedback on the use of the DTBook DTD and identified aspects needing improvement.
Ole Holst Andersen, Danish National Library for the Blind; Jon Beatty, Minnetonka Software, Inc.; Harvey Bingham; Don Breda, American Council of the Blind; Sean Brooks, Canadian National institute for the Blind; John Bryant, National Library Service for the Blind and Physically Handicapped; Curtis Chong, National Federation of the Blind; John Cookson, National Library Service for the Blind and Physically Handicapped; Keith Creasy, American Printing House for the Blind; Tim Curtin, gh; Marisa de Meglio, the DAISY for All Project;, DAISY Consortium; Guillaume du Bourguet, BrailleNet Association; Jim Dust, Telex Communications Corporation; Daniel Farrington, Dolphin Audio Publishing; Dan Germann, LR Sound; Al Gilman; Luis Gutierrez, American Foundation for the Blind; Diana Hiorth Persson, Dolphin Audio Publishing; John Kibitlewski, gh; Jesper Klein, Swedish Library of Talking Books and Braille; Johan Knol, IDUNA Electronics BV; Brad Kormann, National Library Service for the Blind and Physically Handicapped; Kathy Korpolinski, Recording for the Blind & Dyslexic; Dominic Labbé, VisuAide, Inc.; Chris Lehn, Telex Communications Corporation; Lynn Leith, Canadian National Institute for the Blind; Olaf Mittelstaedt, Swiss Library for the Blind and Visually Handicapped; Brandon Nelson, Canadian National Institute for the Blind; Laust Skat Nielsen, Danish National Library for the Blind; Tatsuo Nishizawa, Plextor; Joe Said, gh; Janina Sajka, American Foundation for the Blind; Gregg Savage, Talking Book Publishers, Inc.; Dave Schleppenbach, gh; Per Sennels, National Resource Center for Special Education of the Visually Impaired (Norway); Sheela Sethuraman, CAST; Charles Steaderman; Jeff Suttor, SUN Microsystems; Niels Thögersen, Danish Institute for the Blind; Chris von See, TechAdapt; Christian Wallin, Danish National Library for the Blind; Chris Wilder-Smith, CAST.
(This section is informative.)
This standard establishes specifications for digital talking books (DTBs) for blind, visually impaired, physically handicapped, learning-disabled, or otherwise print-disabled readers. Its purpose is to ensure interoperability across service organizations and vendors providing content and playback systems to the target population.
This standard provides specifications primarily for DTB files and their interrelationships. It also includes specifications for DTB playback devices in two areas: player performance related to file requirements and player behavior in areas defined in user requirements.
(This section is normative.)
The following abbreviations, acronyms, phrases, and terms are used in this standard as defined below. In the following definitions and throughout the standard, bracketed items correspond to entries in section 17, "References to Other Specifications/Documents," where the full URL is provided for each reference.
(This section is informative.)
This standard is based primarily on a variety of widely used standards and specifications, including several from the World Wide Web Consortium and the Open eBook Forum™. Wherever applicable and appropriate standards or specifications existed they were used. The use of these specifications and technologies is intended to promote a fast and consistent adoption of this standard for the target population, while encouraging its extension into mainstream use.
(This section is informative.)
Digital Talking Book files, streams, transformation processes, and players have been designed to present their content to people with a wide range of abilities and disabilities. They are designed to allow presentation in forms other than conventional print, due to the inaccessibility of printed documents to these users. It is in the best interest of users that, to the greatest extent possible, files, streams, transformation processes, and players make information available in as many presentation modes as practical, including human-narrated audio, Braille, synthesized speech, large print with user-specifiable size and text re-wrapping for players with visual display, and text and audio synchronization and other enhancements for persons with learning disabilities. Users will also be greatly benefited if controls on players are readily usable by people with a wide range of manual dexterity.
During the development of this standard, an advisory document, DTB Playback Device Features List, was created. Although it is not a normative part of this standard, player developers will find useful accessibility concepts embodied in it.
In addition to the provisions of this standard, valuable supplemental information is available from the guidelines and techniques produced by the Worldwide Web Consortium's Web Accessibility Initiative. At this time, these documents include:
(This section is normative.)
Not all modes of presentation will be available in all players and documents, but it is strongly recommended that multiple equivalent presentations be made available to users whenever possible. Historically, products marketed to specific user groups with disabilities have sometimes proven unusable. Not all players need to be accessible to all target groups, but any device compliant with this standard must be accessible to the target group for which it is advertised. It is also strongly recommended that DTB production tools and processes be made accessible to persons with disabilities.
(This section is normative.)
This standard is based on the specific versions of the standards and specifications referenced herein, which are used as defined except as noted by this document. Any refinement or replacement of a referenced specification by a newer or different version is not directly applicable to this standard. Conformance to this standard is based on the versions of the standards and specifications in effect at the time of this writing.
(This section is normative.)
Playback systems must support at least UTF-8 and UTF-16 encodings. See section 2.2 of the XML specification [XML].
(This section is informative.)
Implementation of this standard may involve the use of one or more inventions covered by patent rights. It is believed that all companies claiming such rights have agreed to grant a license under such rights as they hold on reasonable and nondiscriminatory terms and conditions to any applicant.
Producers of DTB systems or any component thereof are responsible for obtaining the appropriate licenses for any and all technology they use that is defined by the relevant standards and specifications referenced by this standard. There may be applicable patents of which this standards committee is unaware; it is the responsibility of the implementer to ensure that the implementation is non-infringing.
Issues surrounding the protection of intellectual property embodied in the works distributed as digital talking books are discussed in section 14, "Digital Rights Management."
(This section is informative.)
The maintenance agency designated in Appendix 2 will be responsible for reviewing and acting upon suggestions for modifications to this standard. Questions concerning the implementation of this standard and requests for information should be sent to the maintenance agency.
A list of errata, proposed changes, and maintenance activities related to this standard will be maintained at http://www.daisy.org/z3986/2005/errata.html.
(This section is informative.)
A digital talking book (DTB) is a collection of electronic files arranged to present information to the target population via alternative media, namely, human or synthetic speech, refreshable Braille, or visual display, e.g., large print. When these files are created and assembled into a DTB in accordance with this standard, they make possible a wide range of features such as rapid, flexible navigation; bookmarking and highlighting; keyword searching; spelling of words on demand; and user control over the presentation of selected items (e.g., footnotes, page numbers, etc.). Such features enable readers with visual and physical disabilities to access the information in DTBs flexibly and efficiently, and allow sighted users with learning or reading disabilities to receive the information through multiple senses. For a full discussion of these capabilities, see the "Document Navigation Features List" [Navigation Features], the user requirements document on which this standard was based. A document written during the development of this standard, Theory Behind the DTBook DTD [DTBook Theory], also describes the navigational capabilities of a DTB in some detail. The content of DTBs will range from audio alone, through a combination of audio, text, and images, to text alone.
DTB players will also be produced with a variety of capabilities. The simplest might be portable devices with audio-only capabilities. More complex portable players could include text-to-speech capabilities as well as audio output for recorded human speech. The most comprehensive playback systems are expected to be PC-based, supporting visual and audio output, text-to-speech capability, and output to a Braille display. The Playback Device Features List [Player Features] mentioned above presents the committee's priorities for a range of functions across three types of playback devices.
The files comprising a DTB fall into ten categories, as described below:
(This section is informative.)
The Package File, drawn from the Open eBook Forum™ (OEBF) Publication Structure 1.2, contains administrative information about the DTB, the files that comprise it, and how these files interrelate. This section, drawn largely from the Publication Structure, provides only a brief summary of the function of each section with an example illustrating how it is applied to the DTB. See section 2 of the full OEBF Publication Structure 1.2 for complete details on the Package File.
The Publication Structure describes the major parts of the Package File as follows:
- PACKAGE IDENTITY - a unique identifier for the OEB publication as a whole.
- METADATA - Publication metadata (title, author, publisher, etc.).
- MANIFEST - A list of files (documents, images, style sheets, etc.) that make up the publication. The manifest also includes fallback declarations for files of types not supported by this specification.
- SPINE - An arrangement of documents providing a linear reading order.
- TOURS - A set of alternate reading sequences through the publication, such as selective views for various reading purposes, reader expertise levels, etc.
- GUIDE - A set of references to fundamental structural features of the publication, such as table of contents, foreword, bibliography, etc.
Here is an informal outline of the package file:
<?xml version="1.0"?>
<!DOCTYPE package PUBLIC "+//ISBN 0-9673008-1-9//DTD OEB 1.2 Package//EN"
"oebpkg12.dtd">
<package xmlns="http://openebook.org/namespaces/oeb-package/1.0/"
unique-identifier="foo">
<metadata>...</metadata>
<manifest>...</manifest>
<spine>...</spine>
<tours>...</tours>
<guide>...</guide>
</package>
(This section is normative.)
A DTB conforming to this standard must include exactly one Package File which must be a valid XML 1.0 document conforming to the OEBF Publication Structure 1.2 package DTD (oebpkg12.dtd) and its associated entity reference (oeb12.ent). The full specification, DTD, and entity reference for the OEBF package file are available for download from the OEBF site [OEBF]. The Package File must be named with the extension ".opf". If a DTB spans multiple media units, the identical Package File must be present on each media unit.
A Package File conforming to this standard must comply with all aspects of section 2 of the OEBF Publication Structure 1.2, with the following two exceptions:
spine element may refer only to item elements of media type text/x-oeb1-document. In DTB applications, the spine must only reference items of media type application/smil.
Namespace (xmlns) attributes and their values, although declared as #FIXED,
must be explicitly specified in the document instance. Entity declarations must occur
in the internal DTD subset. See further section 16.1 "General File Conformance
Requirements."
(This section is normative.)
The package must include a value for its unique-identifier
attribute. This is required because more than one dc:Identifier may
be present in a DTB's Package File metadata and the unique-identifier
specifies which dc:Identifier element provides the package's primary
identifier. The value of unique-identifier must match the id attribute
of one and only one dc:Identifier element, which is a descendant of
the package element.
The primary identifier of the DTB must be globally unique.
(This example is informative.)
Example 3.1:
<?xml version="1.0"?>
<!DOCTYPE package PUBLIC "+//ISBN 0-9673008-1-9//DTD OEB 1.2 Package//EN"
"oebpkg12.dtd">
<package xmlns="http://openebook.org/namespaces/oeb-package/1.0/" unique-identifier="uid">
<metadata>
<dc-metadata...>
<dc:Identifier id="uid" scheme="DTB">uk-rnib-db02006
</dc:Identifier>
....
</package>
(This section is normative.)
This portion of the Package File contains the information about a DTB that would normally be found in a library catalog record. It includes data about the DTB itself (e.g., title, author, producer, format, and narrator) as well as information about the source publication (usually a print book) such as publisher, edition, copyright statement, etc.
The Package File must contain exactly one metadata element, which must contain
one and only one dc-metadata element holding Dublin Core [DC]
metadata and must contain supplemental metadata in an x-metadata element.
The x-metadata element must contain at least one instance of the meta
element, which uses name and content attributes to define
its value. (See section 3.2.3, "X-Metadata.")
(This section is normative.)
The use of Dublin Core metadata within a compliant DTB must conform to the following description from the OEBF Publication Structure 1.2:
The
dc-metadataelement contains specific publication-level metadata as defined by the Dublin Core initiative (http://purl.org/dc/). The descriptions below are included for convenience, and the Dublin Core's own definitions take precedence (see http://www.ietf.org/rfc/rfc2413.txt).The
dc-metadataelement can contain any number of instances of any Dublin Core elements. Dublin Core element names begin with the "dc:" prefix followed by a leading uppercase letter. Dublin Core metadata elements may occur in any order; in fact, multiple instances of the same element type (multipledc:Creatorelements, for example) can be interspersed with othermetadataelements without change of meaning.For upwards compatibility, the element
dc-metadatain an OEB package is required to have an attribute of
xmlns:dc="http://purl.org/dc/elements/1.1/"and
xmlns:oebpackage="http://openebook.org/namespaces/oeb-package/1.0/".
Following are brief definitions of the Dublin Core elements. See
the Publication Structure and the Dublin Core itself for more complete descriptions.
The attributes xml:lang and id can be applied to all "dc:..." elements.
Additional attributes can be used with several elements as detailed below. Note
that all Dublin Core element types may be repeated (occur more than once) within
dc-metadata.
dtb:sourcePublisher and dtb:producer.)dc:Creator.dtb:sourceDate and dtb:producedDate.) In format from [ISO8601]; the syntax is YYYY[-MM[-DD]] with a mandatory 4-digit year, an optional 2-digit month, and, if the month is present, an optional 2-digit day of month.dc:Date to describe, for example,
multiple revisions. Best practice is to use dtb:revision and dtb:revisionDate
instead.dc:Format in a DTB conforming to this standard are valid only
if they read "ANSI/NISO Z39.86-2005".package unique-identifier attribute, must include an id.(This section is informative.)
Various schemes are available for identifying digital publications. In the DTB domain, the requirements for an identifier are simply to identify the publication in a manner that is highly likely to be globally unique. A major purpose of the uniqueness requirement is to prevent filename collisions among bookmark files.
To meet this base requirement, a simple DTB id scheme might be used. A DTB identifier under this scheme consists of a hyphen-separated string consisting of a two-letter country code drawn from [ISO 3166], an agency code unique within its country, and an identifier unique within the agency. For example, us-afb-x12345.
This scheme will provide a simple solution to the uniqueness requirement that will serve DTB-publishers' needs in the short term. In the longer term, as the requirements of a global library of alternative format materials become more important, other more sophisticated mechanisms will doubtless be employed.
(This section is normative.)
The following names were developed for the DTB application to supply information that the Dublin Core element set does not cover. These names may only appear within the x-metadata containing element, as values of the name attribute on the meta element. Each x-metadata name below is shown as either "Repeatable" (it may be used more than once) or "Not repeatable". Content producers may introduce other metadata within x-metadata besides those listed below, if needed. However, metadata names shall not begin with the prefix "dtb:" unless defined in this standard. Players must not fail when encountering unknown metadata but must,
at a minimum, ignore it.
audio, text, and image. Media types that are referenced only by NCX, Resource File, or distInfo must not be listed here.dtb:revision. In format from [ISO8601]; the syntax is YYYY[-MM[-DD]] with a mandatory 4-digit year, an optional 2-digit month, and, if the month is present, an optional 2-digit day of month.(This example is informative.)
Example 3.2:
....
<metadata>
<dc-metadata xmlns:dc="http://purl.org/dc/elements/1.1/"
xmlns:oebpackage="http://openebook.org/namespaces/oeb-package/1.0/">
<dc:Title>Revised Standards and Guidelines of
Service for the Library of Congress Network of Libraries for the
Blind and Physically Handicapped 1995</dc:Title>
<dc:Subject>library information networks</dc:Subject>
<dc:Subject>libraries and the physically
handicapped--standards--U.S.</dc:Subject>
<dc:Subject>libraries and the
blind--standards--U.S.</dc:Subject>
<dc:Identifier id="uid"
scheme="DTB">us-nls-db00001</dc:Identifier>
<dc:Identifier
scheme="DOI">10.1000/DX44998</dc:Identifier>
<dc:Creator role="aut">American Library Association.
Association of Specialized and Cooperative Library
Agencies</dc:Creator>
<dc:Publisher>National Library Service for the Blind
and Physically Handicapped, Library of Congress</dc:Publisher>
<dc:Date>2000-06-22</dc:Date>
<dc:Source>0-8389-7797-9</dc:Source>
<dc:Language>en</dc:Language>
<dc:Format>ANSI/NISO Z39.86-2005</dc:Format>
<dc:Description>A document developed to improve library
service for blind and physically disabled persons by providing a
tool for assessing the current status of those services
and for developing long-range plans.</dc:Description>
</dc-metadata>
<x-metadata>
<meta name="dtb:sourceDate" content="1995" />
<meta name="dtb:sourcePublisher"
content="American Library Association" />
<meta name="dtb:sourceRights" content="copyright 1995,
American Library Association" />
<meta name="dtb:narrator" content="Lowenstein, Ralph" />
<meta name="dtb:producer"
content="American Foundation for the Blind" />
<meta name="dtb:multimediaContent" content="audio" />
<meta name="dtb:multimediaType" content="audioNCX" />
<meta name="dtb:totalTime" content="06:22:34.143" />
</x-metadata>
</metadata>
....
(This section is normative.)
The
manifest, which is a child of the package
element, must contain a complete list of all of the files (documents, audio
files, images, style sheets, etc.) that make up a given DTB, including the
package file itself. The manifest shall list only files of
types permitted by this standard. The manifest shall list only
files that are part of the DTB. The distInfo file and any associated audio
changeMsgs (or any other files listed only in the
distInfo file) are not considered part of the DTB and thus shall not be
listed (See section 11, "Packaging Files for Distribution.") The Resource File and
any associated media files are considered part of the DTB and thus shall be
listed. Each file is
referenced by an item element. Each item must
have an href attribute that is the URI of
the referenced file and is unique within
the manifest. This URI must not include fragment
identifiers;
if relative, it is interpreted as relative to the package file itself.
Further,
any relative URIs contained within an XML file listed in the manifest
are considered
to be relative to the referring file.
In addition, each item must have a
media-type attribute containing
the MIME media type of the file, and an id attribute. The
id
is used primarily when a manifest item is referenced by the
spine.
The manifest may also include fallback declarations to
allow players to choose among alternative presentation formats. (See OEBF Publication Structure
for details.) Support for the fallback mechanism is not required by this
standard.
The NCX entry in the Package File manifest must have an id value equal
to "ncx".
The Resource File entry in the Package File manifest must have an id
value equal
to "resource". The order of item
elements within the manifest is not significant.
All media-type attribute values must conform to RFC 2046. In addition, the media-type attribute must have the value of the IANA-registered MIME media type for that type of file, if one exists (see RFC 2048 for information on the registration process for MIME media types). If no MIME media type has been registered for the file type, then the MIME media type recommended in the applicable standard for that file type must be used. If there is no standard MIME media type for the file, then an appropriate "x-" MIME media type must be used, following the rules of RFC 2046. In the case of WAV files, this standard mandates the use of the media type value "audio/x-wav".
For files defined by this standard that are XML documents, this standard defines mandatory, unique media types following RFC 3023: "application/x-dtbncx+xml" for the NCX, "application/x-dtbresource+xml" for the resource file, and "application/x-dtbook+xml" for textual content files.
In addition, producers must use particular file name extensions for all the different kinds of files mentioned in this standard (see table below). These values are case-sensitive. In cases where the file name extension and MIME media type values do not agree, players should consider the MIME media type to take precedence.
The following table summarizes the required file name extensions and MIME media type values for all the different kinds of files that may appear in the package manifest:
| Kind of file | File name extension | MIME media type |
|---|---|---|
| MPEG-4 AAC audio | .mp4 | audio/mpeg4-generic |
| MPEG-1/2 Layer III (MP3) audio | .mp3 | audio/mpeg |
| Linear PCM - RIFF WAVE format audio | .wav | audio/x-wav |
| JPEG image | .jpg | image/jpeg |
| PNG image | .png | image/png |
| Scalable Vector Graphics (SVG) image | .svg | image/svg+xml |
| Cascading Style Sheets (CSS) | .css | text/css |
| SMIL files | .smil | application/smil |
| Package file | .opf | text/xml |
| DTD and DTD fragments (entities or modules) | [no requirement] | application/xml-dtd |
| Navigation Control File (NCX) | .ncx | application/x-dtbncx+xml |
| Textual content files (dtbook) | .xml | application/x-dtbook+xml |
| Resource file | .res | application/x-dtbresource+xml |
(This example is informative.)
A sample manifest for a DTB with audio, structure,
and text follows:
Example 3.3:
....
<manifest>
<item id="opf" href="rs.opf" media-type="text/xml" />
<item id="text" href="rs.xml" media-type="text/x-dtbook+xml" />
<item id="text_style" href="dtbbase.css" media-type="text/css" />
<item id="ncx" href="rs.ncx" media-type="application/x-dtbncx+xml" />
<item id="ncx_style" href="ncx16.css" media-type="text/css" />
<item id="SMIL" href="rs.smil" media-type="application/smil" />
<item id="foreword" href="rs_fwdx.mp3" media-type="audio/mpeg" />
<item id="standards" href="rs_stdx.mp3" media-type="audio/mpeg" />
<item id="appendices" href="rs_app.mp3" media-type="audio/mpeg" />
<item id="index" href="rs_index.mp3" media-type="audio/mpeg" />
<item id="fig_01" href="fig1.png" media-type="image/png" />
<item id="resource" href="rs.res" media-type="application/x-dtbresource+xml" />
<item id="resource_audio" href="res.mp3" media-type="audio/mpeg" />
</manifest>
....
Here is a manifest for an audio-only version of the
above DTB where separate SMIL files were created for
each segment of the book.
Example 3.4:
....
<manifest>
<item id="opf" href="rs.opf" media-type="text/xml" />
<item id="ncx" href="rs.ncx" media-type="application/x-dtbncx+xml" />
<item id="foreword" href="rs_fwdx.mp3" media-type="audio/mpeg" />
<item id="standards" href="rs_stdx.mp3" media-type="audio/mpeg" />
<item id="appendices" href="rs_app.mp3" media-type="audio/mpeg" />
<item id="index" href="rs_index.mp3" media-type="audio/mpeg" />
<item id="SMIL1" href="rsfwd.smil" media-type="application/smil" />
<item id="SMIL3" href="rsapp.smil" media-type="application/smil" />
<item id="SMIL4" href="rsind.smil" media-type="application/smil" />
<item id="SMIL2" href="rsstd.smil" media-type="application/smil" />
</manifest>
....
(This section is normative.)
To assure interoperability when transporting DTBs between various locales and platforms, characters in file names must be restricted to the alphanum definition of [RFC2396], and a subset of the RFC2396 mark definition. This effectively reduces allowed characters to [A-Za-z0-9._-].
The following definition "filename" identifies in EBNF form which characters are allowed in file names. The definition "foldername" identifies allowed characters in folder names, when folders are used in path specifications of URIs that reference members of the DTB file set.
digit ::= [#x0030-#x0039] lowalpha ::= [#x0061-#x007A] upalpha ::= [#x0041-#x005A] alphanum ::= digit|lowalpha|upalpha hyphen ::= [#x002D] underscore ::= [#x005F] period ::= [#x002E] filename ::= (alphanum|hyphen|underscore|period)+ foldername ::= (alphanum|hyphen|underscore)+
(This section is informative.)
These restrictions should be regarded as an interim solution. As soon as a global recommendation or standard for internationalized resource identification is established, consideration for adoption will be a high priority.
(This section is normative.)
All URIs referencing fileset members are case sensitive.
Fileset members must not be given names that result in multiple identical names following case normalization.
(This section is normative.)
The spine, a child of the package element, shall
consist of a list of one or more itemref elements whose order defines
the default linear reading order for the DTB. Each itemref must
contain an idref which points to the id of a SMIL file
listed in the manifest. Only SMIL files can be referenced by itemrefs in the spine. The itemrefs must be listed in the spine in the order in which the SMIL files are to be presented. A player must consult the
spine when it reaches the end of a SMIL file to determine which file
to render next.
(The following examples are informative.)
The first
of the following examples shows the spine that corresponds to the first of the two
manifest examples above.
Example 3.5:
<spine>
<itemref idref="SMIL" />
</spine>
The following spine matches the second manifest example above. The correct
reading order is presented here. Note that it does not match the order of files in the
manifest where order is not significant.
Example 3.6:
<spine>
<itemref idref="SMIL1" />
<itemref idref="SMIL2" />
<itemref idref="SMIL3" />
<itemref idref="SMIL4" />
</spine>
(This section is informative.)
The tours element is an optional child of the package element.
The OEBF Publication Structure describes tours
as follows: "Much as a tour guide might assemble points of interest into a set
of sightseers' tours, a content provider may assemble selected parts of a publication
into a set of tours to enable convenient navigation. ... Reading systems may
use tours to provide various access sequences to parts of the publication, such
as selective views for various reading purposes, reader expertise levels, etc."
Because of inherent differences between the structures of a DTB and the OEBF
tours, it is not feasible to implement tours in a DTB prepared
in accordance with this standard. If a producer wishes to provide the functionality
described above, it may partially achieve it by producing customized navLists
in the NCX.
(This section is normative.)
Compliant players are not required to support tours.
(This section is informative.)
As specified in the OEBF Publication Structure, the guide,
a child of the package element, lists the key structural features
of the DTB, such as the table of contents, introduction, bibliography, etc.
to enable playback devices to provide convenient access to them. Because DTBs
include a mandatory NCX that satisfies a more rigorous and detailed access requirement,
the guide is not expected to be used in DTBs.
(This section is normative.)
Compliant players are not required to support guides.
(This section is normative.)
This standard defines an XML 1.0 Document Type Definition
-- DTBook -- for markup of the textual content files of books and other publications
presented in digital talking book format. To be compliant with this standard,
a textual content file of a DTB must be a valid XML file
conforming to dtbook-2005-1.dtd, which can be found in Appendix
1, "DTBook
DTD." See Section 3.3, "Manifest"
for filename extension requirements. The version and xmlns attributes on the dtbook element must be explicitly specified in the document instance, using values drawn from the above-named DTD. Entity declarations must occur in the internal DTD subset. See further section 16.1 "General File Conformance Requirements."
A DTB that includes textual content will, in most cases, contain only one textual content file. However, when necessary (with a very large book, for example), a DTB can contain multiple textual content files, each of which must be valid to the DTBook DTD.
DTB content producers may extend the base DTD by including one or more new elements or full modules for special situations. To remain conformant with this standard, such extensions of the DTD must employ the mechanisms specified by XML 1.0. See section 4.2.2, "Modular Extension of the DTD."
Two
metadata items must be present in the <head> of compliant textual content
files, contained in a <meta> element: dtb:uid and dc:Title. dtb:uid
is the globally unique identifier for the DTB. The value is the same as that
of the dc:Identifier element referenced by the package file's
unique-identifier element. See section 3.1, "Package Identity."
dc:Title contains the title of the DTB. Inclusion of the full range of applicable
Dublin Core elements is recommended, to make a DTBook document more useful
as stand-alone content.
(This section is informative.)
A document developed during the creation of this standard, Theory Behind the DTBook DTD [DTBook Theory], discusses the rationale underlying the DTBook element set and the benefits it provides to digital talking book applications.
Two documents external to this standard provide detailed information on the use of the element set. First, an expanded version of the DTD, in HTML format, (see [DTBook HTML]) provides full detail on each element, describing where it can be used and which elements can be used within it, along with an expanded list of attributes.
Second, a comprehensive set of guidelines for applying DTBook markup is available from the DAISY Consortium. These Structure Guidelines [StructGuide] describe the correct application of the DTBook element set, emphasize the importance of capturing the structure of the text content, and provide detailed examples of the use of all DTBook elements.
The DTBook element set has considerable application outside of the digital talking book as well. It was designed to enable the production of documents in a variety of accessible formats. At least one U.S. Braille translation software package has implemented a facility that imports DTBook documents and automatically translates and formats them in Grade 2 Braille. It is expected that similar automated processes will be developed for converting properly marked-up documents into large print and for rendering DTBook documents in Braille, synthetic speech, and large print "on the fly." Finally, an attribute called "showin" is incorporated in the DTBook element set to control the display of selected segments of a DTBook document. For example, descriptions of a graph might vary between Braille and large print editions; "showin" could allow only the appropriate version to show in each edition, although both would be present in the DTBook document.
This standard does not mandate the degree of markup to be applied to a textual content file. However, the richer the markup, the greater the functionality available to the reader.
For more information on XML 1.0 markup and DTD usage, see the W3C XML site [XML].
(This section is normative.)
To ensure efficient player operation with DTBs containing textual content files, the smilref attribute must be present and non-empty for each element in the textual content file referenced by a SMIL file. The smilref value shall normally be the URI of the SMIL time container (par or seq) containing the media object that references a given element. However, in a text-only DTB consisting of a sequence of text media objects, smilref contains the URI of the media object that references the element. The smilref attribute permits the DTB player to resume SMIL-based playback following text-based navigation, full-text searches, etc.
(This section is informative.)
The DTBook DTD includes a base set of elements for use in marking up a broad range of material. Additional modules containing elements for specialized applications such as poetry, plays, dictionaries, mathematics, etc. can be "invoked" from within a DTBook document when needed, as described below.
A DTBook document is an XML application. Therefore
it should begin with the XML declaration identifying the version of XML, and
the optional character set encoding. (See Appendix 1, "DTBook
DTD"
for more information.)
<?xml version="1.0" encoding="UTF-8" ?>
This is followed by the document type declaration:
<!DOCTYPE dtbook PUBLIC "-//NISO//DTD dtbook 2005-1//EN" "http://www.daisy.org/z3986/2005/dtbook-2005-1.dtd">
For discussion of other ways of expressing the DOCTYPE, see section 2.3 of the "DTBook DTD" listed in Appendix 1.
A book can invoke other DTDs or modules to augment the DTBook DTD by adding instructions in square brackets before the concluding ">" of the document type declaration. Such instructions in square brackets are called the "internal subset of declarations." For example:
<!DOCTYPE dtbook PUBLIC "-//NISO//DTD dtbook 2005-1//EN"
"dtbook-2005-1.dtd"
[
<!ENTITY % dramaModule SYSTEM "drama.dtd" >
%dramaModule;
<!ENTITY % externalblock "| drama">
<!ENTITY % externalinline "| stagedir">
]>
The first line of the internal subset declares an entity known as "dramaModule" and provides the URI where that module can be found. The second line invokes this entity, that is "brings it into" the current document, just as the DOCTYPE declaration invoked the base DTD (dtbook-2005-1.dtd). The third line declares the entity "% externalblock" and gives it the value "drama". Since dtbook-2005-1.dtd contains an entity of the same name, and the internal subset overrules the base (external) DTD (dtbook-2005-1) in areas of conflict, everywhere in dtbook-2005-1 where "%externalblock;" appears (that is, wherever block elements are allowed), the value "drama" is added. Since drama is the root element in the drama module, the full drama module can be used there. Similarly, the last line effectively allows the element stagedir to be used anywhere "%externalinline;" is allowed in dtbook-2005-1 (that is, wherever inline elements can be used).
More than one module may be needed and included in a book. In the following example, both a poetry and drama module are invoked, as well as one inline element (stagedir) from the drama module.
[
<!ENTITY % poemModule "http://www.xyz.org/poem.dtd" >
%poemModule;
<!ENTITY % dramaModule "http://www.xyz.org/drama.dtd" >
%dramaModule;
<!ENTITY % externalblock "| poem | drama" >
<!ENTITY % externalinline "| stagedir">
]>
See section 3 of the "DTBook DTD" (see Appendix 1) for a more detailed discussion of this issue.
(This section is normative.)
A set of audio file formats is listed below. A compliant audio player must be capable of decoding at least one of the formats listed. It is strongly recommended that players be able to decode all listed formats. Content compliant with this standard must be delivered in one of the formats below, or any mixture of them.
It is permissible for parts of a single book to be encoded in different audio formats. For example, a producer may choose to encode a lengthy bibliography at a lower bit rate or with a different codec than the main body of the book. Players must support transitions between differently encoded sections smoothly. There is no restriction on the granularity of these parts, i.e. they may occur at any point in the SMIL presentation.
Support for multi-channel rendering is not required. Stereo signals must be recognized and rendered at least in monaural format.
A compliant DTB player that provides audio output should be capable of decoding the following audio formats:
See Section 3.3, "Manifest" for filename extension requirements.
While the ISO standards for MP3 and AAC require support for variable bit rate playback, players compliant with this standard are only required to support constant bit rate playback.
Players must support sample rates of 44.1, 22.05, and 11.025 kHz at a depth of 16 bits per sample. Compressed audio must be encoded such that the output sampling rate is restricted to one of the above three rates.
(This section is normative.)
Audio players capable of recording and exporting audio notes for bookmarks and highlights must support encoding in the following format or one of the formats specified in section 5.1. Audio players capable of importing bookmarks and highlights must support decoding of the following format.
(This section is normative.)
Images included in DTBs must be presented in one or more of the following formats: JPEG (JFIF V 1.02) [JPEG], PNG [RFC 2083], or Scalable Vector Graphics [SVG]. Compliant playback devices that support image display must be capable of displaying JPEG and PNG; support for SVG is recommended. Appendix 8 of the SVG specification addresses accessibility issues. See Section 3.3, "Manifest" for filename extension requirements.
(This section is informative.)
The Synchronized Multimedia Integration Language (SMIL 2.0) [SMIL] was developed by the World Wide Web Consortium as a standard for definition and playback of multimedia presentations over the Internet. SMIL defines the sequence of playback for one or more media objects. In the case of DTBs, the primary media objects are audio and textual content files; SMIL provides for their parallel and synchronized presentation. Any DTB constructed using SMIL, and utilizing content encoded in standard text and audio media types, is playable on any device or platform which has implemented a SMIL-conformant player of the same or later SMIL version, so long as the necessary audio and textual rendering decoders are present and no system for intellectual property protection restricts access.
What distinguishes a DTB playback system from a basic SMIL player is the inclusion of specific navigation and presentational capabilities set out in the user requirements for DTBs ([Navigation Features]). These capabilities can use information from an NCX file, from the textual content, and/or from the SMIL file itself. The key to this information is the inclusion of unique identifiers within the textual content (when present) and SMIL files. Audio files are indexed by time-based positions and in themselves contain no embedded semantic structure. To provide semantic structure to audio content, it is necessary to associate time-points in the audio file with the corresponding position within the textual content. This is achieved using SMIL through the pairing of a pointer to a specific position within a textual content file (referenced by a URI) with its corresponding time position in the audio content. In the case of the DTB SMIL application, each synchronization point within the SMIL file is assigned a unique identifier. The presence of these identifiers within both the textual content and the SMIL allows navigation to occur by several different methods, as determined by the playback system.
SMIL incorporates a control structure called customTests, which allows SMIL authors to identify by class selected elements of a document (e.g., notes, page numbers, line numbers). The playback device can then expose to the user the presence of these classes and allow the user to select whether a given class of elements is to be read or skipped over during sequential playback.
The duration of time containers in SMIL presentations may be determined by the duration of child media objects and time containers, or by recognized events that signal the end of a time container. DTB producers may elect to create content that incorporates pauses in the presentation to allow for users to examine related materials or to work on a problem, for example. Users, once they complete the related task, will signal that playback can continue by an appropriate mechanism in the player user interface.
Pauses in sequential presentation are authored by
specifying a time container with an end attribute value
that indicates that the container will remain active until
the occurrence of a user event, such as the pressing of a
resume or play button, or until the end of a specified duration.
Escapable structures are implemented by a user initiated escape event. Structures that are escapable are wrapped by a time container that will play until either the normal end time of the child time container(s) or the occurrence of a user escape event, whichever comes first. In this case, the DTB player that supports escapability may provide a user interface mechanism for indicating that the user has requested to escape from the current structure.
The DTB producer determines granularity of the synchronization events. Synchronization events can be limited to the primary structural elements (those indicated in the NCX) or can be augmented in books with full textual content to include synchronization down to paragraph, sentence, or even word level. The requirement for this level of synchronization is that the textual content includes mark-up tags for the desired elements and that those elements include unique identifiers that can be referenced in the SMIL files.
The SMIL file for a DTB typically will consist of a sequence of parallel events
(e.g., text and audio (and possibly image) events occurring simultaneously).
SMIL represents this structure through the use of the "time containers" seq
(sequence of media objects) and par (parallel time grouping in which
multiple media objects play back at the same time). A simple form of DTB SMIL
file would be as follows, where the three pars shown are played one
after the other, and the text and audio content referenced in each par are rendered simultaneously:
<smil> ... <seq> <par><text.../><audio.../></par> <par><text.../><audio.../></par> <par><text.../><audio.../><img.../></par> </seq> .... </smil>
(This section is informative.)
Synchronization of media objects in this standard is based on the SMIL 2.0 specification. Developers are requested to reference SMIL 2.0 [SMIL] for complete background and details. Only a small subset of the SMIL specification is used in this application, drawing from the following modules, which are grouped by functional area. Modules marked with asterisks are used in whole or in part in this application; the others are not used but are included because they are part of a core set of modules required for host language conformance under W3C modularization guidelines.
The modules mentioned above can be combined, using W3C modularization guidelines, to form a profile specific to DTB applications. Section 2 of the SMIL specification, "The SMIL 2.0 Modules," describes this process in detail.
(This section is normative.)
To simplify validation using commonly available parsers and to lessen the complexity of determining content models and applicable attribute lists, a DTB-Specific SMIL DTD is included in this standard in Appendix 1. This DTD includes only those elements and attributes from the modules listed above that are required for the DTB application. In addition, it is more restrictive than the SMIL modules in that some attributes are required in the DTB application when they are only implied in the SMIL modules.
A compliant DTB must contain at least one SMIL file. All SMIL files included
in a DTB must be valid XML documents conforming to dtbsmil-2005-1.dtd. See Section 3.3, "Manifest"
for filename extension requirements. The xmlns attribute on the smil element must be explicitly specified in the document instance, using the value drawn from the above-named DTD. Entity declarations must occur in the internal DTD subset. See further section 16.1 "General File Conformance Requirements."
Time containers (seqs or pars) within SMIL files must contain
ids. Media objects (audio, text, and img) may also
contain ids, although this practice will generally be limited to single-medium
DTBs. See section 7.4.10, "Text-Only DTBs."
In the textual content file, each segment to be synchronized (e.g., heading,
paragraph, list item, etc.) must be contained within an element carrying a unique
id to which the corresponding SMIL segment points. In addition, any textual
content file element referenced by a SMIL file must include a smilref attribute
specifying the URI of the time container or media object that references it.
The smilref value will normally be the URI of the SMIL time container
containing the media object that references a given element. However, in a text-only
DTB consisting of a sequence of text media objects, smilref shall contain
the URI of the referencing media object itself. See section 4.2.1, "DTBook
Markup Related to SMIL."
It is strongly recommended that the SMIL file(s) have a level of granularity matching that of the textual content file. That is, if the textual content file is marked up to the paragraph level, the SMIL file(s) should include synchronization to the paragraph level.
All time offsets in SMIL files (and all other applicable DTB files, e.g., NCX clipBegin/clipEnd, bookmark timeOffsets, etc.), are based on normal play speed. In order to maintain synchronization, a player must process time offsets independently of actual playback speed.
(This section is informative.)
As mentioned above, the DTB application uses only a portion of the elements and attributes that make up the modules in the DTB SMIL Profile. Playback devices compliant with this standard need support only the following SMIL elements and attributes, which make up the DTB-Specific SMIL DTD.
smil. The smil element contains exactly one head and exactly one body.<!ELEMENT smil (head, body) ><smil>...content...</smil> meta element), optional layout,
and optional customAttributes.<!ELEMENT head (meta*, (layout, meta*)?, (customAttributes,meta*)?)
><head>...content...</head><smil> <meta ...attributes... /><!ELEMENT meta EMPTY ><head> region elements it
contains) where on a visual, audio, or tactile rendering space various producer-defined
elements, e.g., figures, text, footnotes, etc. are displayed.<!ELEMENT layout (region)+ ><layout>...content...</layout><head>