ISO/IEC 23736-2:2020

INTERNATIONAL ISO/IEC
STANDARD 23736-2
First edition
2020-02
Information technology — Digital
publishing — EPUB 3.0.1 —
Part 2:
Publications
Technologies de l'information — Publications numériques — EPUB
3.0.1 —
Partie 2: Publications
Reference number
©
ISO/IEC 2020
© ISO/IEC 2020
All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may
be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting
on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address
below or ISO’s member body in the country of the requester.
ISO copyright office
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CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO/IEC 2020 – All rights reserved

Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are
members of ISO or IEC participate in the development of International Standards through technical
committees established by the respective organization to deal with particular fields of technical activity.
ISO and IEC technical committees collaborate in fields of mutual interest. Other international
organizations, governmental and non‐governmental, in liaison with ISO and IEC, also take part in the
work.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular, the different approval criteria needed for the
different types of document should be noted (see www.iso.org/directives).
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. ISO and IEC shall not be held responsible for identifying any or all such patent rights.
Details of any patent rights identified during the development of the document will be in the
Introduction and/or on the ISO list of patent declarations received (see www.iso.org/patents) or the IEC
list of patent declarations received (see http://patents.iec.ch).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation of the voluntary nature of standards, the meaning of ISO specific terms and
expressions related to conformity assessment, as well as information about ISO's adherence to the World
Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT),
see www.iso.org/iso/foreword.html.
This document was prepared by the World Wide Web Consortium (W3C) (as EPUB Publications 3.0.1)
and drafted in accordance with its editorial rules. It was adopted, under the JTC 1 PAS procedure,
by Joint Technical Committee ISO/IEC JTC 1, Information technology.
A list of all parts in the ISO/IEC 23736 series can be found on the ISO websitte.e
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www.iso.org/members.html.
© ISO/IEC 2020 – All rights reserved iii

EPUB Publications 3.0.1
Recommended Specification 26 June 2014
THIS VERSION
http://www.idpf.org/epub/301/spec/epub-publications-20140626.html
LATEST VERSION
http://www.idpf.org/epub3/latest/publications
PREVIOUS VERSION
http://www.idpf.org/epub/301/spec/epub-publications-20140228.html
A diff of changes from the previous version is also available.
Please refer to the errata for this document, which may include some normative corrections.
All rights reserved. This work is protected under Title 17 of the United States Code. Reproduction and
dissemination of this work with changes is prohibited except with the written permission of the International
Digital Publishing Forum (IDPF).
EPUB is a registered trademark of the International Digital Publishing Forum.
Editors
Markus Gylling, International Digital Publishing Forum (IDPF)
William McCoy, International Digital Publishing Forum (IDPF)
Matt Garrish, Invited Expert
TABLE OF CONTENTS
1. Overview
1.1. Purpose and Scope
1.2. Terminology
1.3. Typographic Conventions
1.4. Conformance Statements
2. EPUB Publications
2.1. Content Conformance
2.2. Reading System Conformance
3. Package Documents
3.1. Introduction
3.2. Content Conformance
3.3. Reading System Conformance
3.4. Package Document Definition
3.4.1. The package Element
3.4.2. The metadata Element
3.4.3. The DCMES identifier Element
3.4.4. The DCMES title Element
3.4.5. The DCMES language Element
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ISO/IEC 23736-1:2020(E)
3.4.6. The DCMES Optional Elements
3.4.7. The meta Element
3.4.8. The meta Element (OPF2) [OBSOLETE]
3.4.9. The link Element
3.4.10. The manifest Element
3.4.11. The item Element
3.4.12. The spine Element
3.4.13. The itemref Element
3.4.14. The guide Element [DEPRECATED]
3.4.15. The bindings Element
3.4.16. The mediaType Element
3.4.17. The collection Element
4. Package Metadata
4.1. Publication Identifiers
4.1.1. Unique Identifier
4.1.2. Release Identifier
4.2. Vocabulary Association Mechanisms
4.2.1. Overview
4.2.2. Default Vocabulary
4.2.3. Reserved Prefixes
4.2.4. The prefix Attribute
4.2.5. The property Data Type
4.2.5.1. Syntax
4.2.5.2. Processing
4.3. Package Metadata Vocabulary
4.3.1. Overview
4.3.2. Metadata meta Properties
4.3.2.1. Publication
4.3.2.2. Rendering
4.3.3. Metadata link Properties
4.3.4. Manifest item Properties
4.3.5. Spine itemref Properties
4.4. Publication Rendering
4.4.1. General Properties
4.4.1.1. Overview
4.4.1.2. The rendition:flow Property
4.4.1.2.1. Usage
4.4.1.2.2. Allowed values
4.4.1.2.3. Spine Overrides
4.4.1.3. The rendition:align-x-center Property
4.4.2. Fixed-Layout Properties
4.4.2.1. Overview
4.4.2.2. The rendition:layout Property
4.4.2.2.1. Usage
4.4.2.2.2. Allowed values
4.4.2.2.3. Spine Overrides
4.4.2.3. The rendition:orientation property
4.4.2.3.1. Usage
4.4.2.3.2. Allowed values
4.4.2.3.3. Spine Overrides
4.4.2.4. The rendition:spread Property
4.4.2.4.1. Usage
4.4.2.4.2. Allowed values
4.4.2.4.3. Spine Overrides
4.4.2.5. The page-spread-* Properties
4.4.2.6. The rendition:viewport Property
5. Publication Resources
5.1. Core Media Types
5.2. Restrictions and Fallbacks
5.2.1. Foreign Resource Restrictions
5.2.2. Manifest Fallbacks
5.3. Publication Resource Locations
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5.4. XML Conformance
A. Package Document Schema
B. The application/oebps-package+xml Media Type
C. Acknowledgements and Contributors
References
› 1 Overview
› 1.1 Purpose and Scope
This section is informative
This specification, EPUB Publications 3.0.1, defines semantics and conformance requirements for
EPUB® Publications, including the format of the Package Document that describes each Rendition of
the content and rules for how this document and other Publication Resources are associated to
create a conforming EPUB Publication.
This specification is one of a family of related specifications that compose EPUB 3, the third major
revision of an interchange and delivery format for digital publications based on XML and Web
Standards. It is meant to be read and understood in concert with the other specifications that make up
EPUB 3:
The EPUB 3 Overview [EPUB3Overview], which provides an informative overview of EPUB and
a roadmap to the rest of the EPUB 3 documents. The Overview should be read first.
EPUB Content Documents 3.0.1 [ContentDocs301], which defines profiles of XHTML, SVG and
CSS for use in the context of EPUB Publications.
EPUB Open Container Format (OCF) 3.0.1 [OCF301], which defines a file format and
processing model for encapsulating a set of related resources into a single-file (ZIP) EPUB
Container.
EPUB Media Overlays 3.0.1 [MediaOverlays301], which defines a format and a processing
model for synchronization of text and audio.
This specification supersedes EPUB Publications 3.0 [Publications30]. Refer to [EPUB3Changes] for
information on differences between this specification and its predecessor.
› 1.2 Terminology
EPUB Publication
A collection of one or more Renditions conforming to this specification and its sibling
specifications , packaged in an EPUB Container.
An EPUB Publication typically represents a single intellectual or artistic work, but this
specification and its sibling specifications do not circumscribe the nature of the content.
Rendition
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ISO/IEC 23736-1:2020(E)
A logical document entity consisting of a set of interrelated resources representing one
rendering of an EPUB Publication.
Default Rendition
The Rendition listed in the first rootfile element in the Container – META-
INF/container.xml [OCF301] file.
Publication Resource
A resource that contains content or instructions that contribute to the logic and rendering of
at least one Rendition of an EPUB Publication. In the absence of this resource, the EPUB
Publication might not render as intended by the Author. Examples of Publication Resources
include a Rendition's Package Document, EPUB Content Document, EPUB Style Sheets,
audio, video, images, embedded fonts and scripts.
With the exception of the Package Document itself, the Publication Resources required to
render a Rendition are listed in that Rendition's manifest and bundled in the EPUB
Container file (unless specified otherwise in Publication Resource Locations).
Examples of resources that are not Publication Resources include those identified by the
Package Document link element and those identified in outbound hyperlinks that resolve
outside the EPUB Container (e.g., referenced from an [HTML5] a element href attribute).
Foreign Resource
A Publication Resource that is not a Core Media Type. A Foreign Resource requires at
least one fallback, as defined in Restrictions and Fallbacks.
Core Media Type Resource
A Publication Resource that is a Core Media Type and may therefore be included in the
EPUB Publication without the provision of fallbacks.
EPUB Content Document
A Publication Resource that conforms to one of the EPUB Content Document definitions
(XHTML or SVG).
An EPUB Content Document is a Core Media Type, and may therefore be included in the
EPUB Publication without the provision of fallbacks.
XHTML Content Document
An EPUB Content Document conforming to the profile of [HTML5] defined in XHTML
Content Documents [ContentDocs301] .
XHTML Content Documents use the XHTML syntax of [HTML5].
SVG Content Document
An EPUB Content Document conforming to the constraints expressed in SVG Content
Documents [ContentDocs301] .
EPUB Navigation Document
A specialization of the XHTML Content Document, containing human- and machine-
readable global navigation information, conforming to the constraints expressed in EPUB
Navigation Documents [ContentDocs301] .
Scripted Content Document
4 © ISO/IEC 2020 – All rights reserved

An EPUB Content Document that includes scripting or an XHTML Content Document that
contains HTML5 forms elements.
Refer to Scripted Content Documents [ContentDocs301] for more information.
Top-level Content Document
An EPUB Content Document referenced from the spine, whether directly or via a fallback
chain [Publications301] .
Fixed-Layout Document
An EPUB Content Document directly referenced from the spine that has been designated
pre-paginated in the Package Document, as defined in The rendition:layout Property
[Publications301] .
The dimensions to use for rendering Fixed-Layout Documents are defined in Fixed-Layout
Documents [ContentDocs301] .
Synthetic Spread
The rendering of two adjacent pages simultaneously on a device screen.
Core Media Type
A set of Publication Resource types for which no fallback is required. Refer to Publication
Resources for more information.
Package Document
A Publication Resource carrying bibliographical and structural metadata about a given
Rendition of an EPUB Publication, as defined in Package Documents .
Unique Identifier
The Unique Identifier is the primary identifier for an EPUB Publication, as identified by the
unique-identifier attribute. The Unique Identifier may be shared by one or many
Renditions of the same EPUB Publication that conform to the EPUB standard and embody
the same content.
The Unique Identifier is less granular than the ISBN. However, significant revision,
abridgement, etc. of the content requires a new Unique Identifier.
Release Identifier
The Release Identifier allows any instance of an EPUB Publication to be compared against
another to determine if they are identical, different versions, or unrelated.
Refer to Release Identifier for more information.
Manifest
A list of all Publication Resources that constitute the given Rendition of a EPUB
Publication.
Refer to manifest for more information.
Spine
An ordered list of Publication Resources, typically EPUB Content Documents, representing
the default reading order of the given Rendition of an EPUB Publication.
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ISO/IEC 23736-1:2020(E)
Refer to spine for more information.
Media Overlay Document
An XML document that associates the XHTML Content Document with pre-recorded audio
narration in order to provide a synchronized playback experience, as defined in
[MediaOverlays301].
Text-to-Speech (TTS)
The rendering of the textual content of an EPUB Publication as artificial human speech
using a synthesized voice.
EPUB Style Sheet (or Style Sheet)
A CSS Style Sheet conforming to the CSS profile defined in EPUB Style Sheets
[ContentDocs301] .
Viewport
The region of an EPUB Reading System in which the content of an EPUB Publication is
rendered visually to a User.
CSS Viewport
A Viewport capable of displaying CSS-styled content.
EPUB Container (or Container)
The ZIP-based packaging and distribution format for EPUB Publications defined in
[OCF301].
Author
The person(s) or organization responsible for the creation of an EPUB Publication, which is
not necessarily the creator of the content and resources it contains.
User
An individual that consumes an EPUB Publication using an EPUB Reading System.
EPUB Reading System (or Reading System)
A system that processes EPUB Publications for presentation to a User in a manner
conformant with this specification and its sibling specifications .
User Agent
A client or application that consumes generic HTML (e.g., Web browser, screen readers)
› 1.3 Typographic Conventions
The following typographic conventions are used in this specification:
markup
All markup (elements, attributes, properties), code (JavaScript, pseudo-code), machine
processable values (string, characters, media types) and file names are in red-orange
monospace font.
6 © ISO/IEC 2020 – All rights reserved

markup
Links to markup and code definitions are underlined and in red-orange monospace font. Only
the first instance in each section is linked.
http://www.idpf.org/
URIs are in navy blue monospace font.
hyperlink
Hyperlinks are underlined and in blue.
[reference]
Normative and informative references are enclosed in square brackets.
Term
Terms defined in the Terminology are in capital case.
Term
Links to term definitions have a dotted blue underline. Only the first instance in each section is
linked.
Normative element, attribute and property definitions are in blue boxes.
Informative markup examples are in white boxes.
NOTE
Informative notes are in yellow boxes with a "Note" header.
CAUTION
Informative cautionary note are in red boxes with a "Caution" header.
› 1.4 Conformance Statements
The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY,
and OPTIONAL in this document are to be interpreted as described in [RFC2119].
All sections of this specification are normative except where identified by the informative status label
"This section is informative". The application of informative status to sections and appendices applies
to all child content and subsections they may contain.
All examples in this specification are informative.
© ISO/IEC 2020 – All rights reserved 7

ISO/IEC 23736-1:2020(E)
› 2 EPUB Publications
This section defines conformance requirements for EPUB Publications and EPUB Reading Systems
at the Rendition level. Conformance requirements particular to specific Publication Resources and
processing contexts are located in the specifications referenced herein.
› 2.1 Content Conformance
Each Rendition of an EPUB Publication MUST meet all of the following criteria:
All Publication Resources
›
All Publication Resources MUST be listed in the Package Document (as defined in manifest),
adhere to the constraints for Core Media Types and Fallback and be located as per Publication
Resource Locations.
The Package Document
›
It MUST contain exactly one Package Document, which MUST conform to the content
requirements defined in Package Document — Content Conformance.
Content Documents
›
It MUST contain at least one EPUB Content Document conformant to the content requirements
defined in EPUB Content Documents [ContentDocs301] .
The EPUB Navigation Document
›
It MUST contain exactly one EPUB Navigation Document conformant to the content
requirements defined in EPUB Navigation Documents — Content Conformance
[ContentDocs301] .
EPUB Style Sheets
›
It MAY contain zero or more EPUB Style Sheets conformant to the content requirements
defined in EPUB Style Sheets — Content Conformance [ContentDocs301] .
EPUB Pronunciation Lexicons
›
It MAY contain zero or more PLS Documents conformant to the content requirements defined in
PLS Documents — Content Conformance [ContentDocs301] .
Media Overlay Documents
›
It MAY contain zero or more Media Overlay Documents conformant to the content requirements
defined in [MediaOverlays301].
Additional Publication Resources
›
It MAY contain zero or more Publication Resources in addition to those listed above, each of
which MUST adhere to the requirements in All Publication Resources.
Container
8 © ISO/IEC 2020 – All rights reserved

›
It MUST be packaged in a EPUB Container as defined in [OCF301].
› 2.2 Reading System Conformance
An EPUB Reading System MUST meet all of the following criteria:
EPUB 3 Processing
›
It MUST process the EPUB Container as defined in [OCF301].
›
It MUST process the Package Document as defined in Package Document — Reading System
Conformance, and honor all presentation logic expressed through the Package Document (e.g.,
the reading order, fallback chains, bindings, page progression direction and fixed layouts).
›
It MUST NOT fail catastrophically if it encounters two distinct EPUB Publications with the same
Unique Identifier.
›
Unless specified as conditional behavior in this section, it MUST support all Core Media Type
Resources.
›
It MAY support an arbitrary set of Foreign Resource types, and MUST process fallbacks for
unsupported Foreign Resources as defined in Restrictions and Fallbacks if not.
›
It MUST process XHTML Content Documents as defined in XHTML Content Documents —
Reading System Conformance [ContentDocs301] .
›
It MUST process SVG Content Documents as defined in SVG Content Documents — Reading
System Conformance [ContentDocs301] .
›
If it has a CSS Viewport , it MUST support visual rendering of XHTML Content Documents as
defined in EPUB Style Sheets — Reading System Conformance [ContentDocs301] .
›
If it has the capability to render raster images, it MUST support the raster image Core Media
Types.
›
If it has the capability to render vector images, it MUST support the vector image Core Media
Types.
›
If it has the capability to render pre-recorded audio, it MUST support the MP3 audio Core Media
Type, SHOULD support the MP4 audio Core Media Type and SHOULD support Media Overlays
[MediaOverlays301].
›
If it supports Text-to-Speech (TTS) rendering, it SHOULD support PLS Documents
[ContentDocs301] , the CSS3 Speech features of the EPUB CSS Profile [ContentDocs301] and
SSML attributes [ContentDocs301] in XHTML Content Documents.
›
It MUST support the EPUB Canonical Fragment Identifiers scheme [EPUBCFI] for linking, and
MAY support additional linking schemes as defined in the EPUB Linking Scheme Registry.
NOTE
It is recommended that Reading Systems support at least one of the [H.264] and [VP8]
video codecs, but this is not a conformance requirement; a Reading System may support
no video codecs at all. Content creators and Reading System developers should take
© ISO/IEC 2020 – All rights reserved 9

ISO/IEC 23736-1:2020(E)
into consideration factors such as breadth of adoption, video playback quality, and
technology usage royalty requirements when making a choice to include or implement
video in either (or potentially, both) formats.
Backward Compatibility
›
It SHOULD process EPUB version 2 Publications as defined in [OPF2], [OPS2] and [OCF2].
›
It MUST attempt to process any given Rendition of an EPUB Publication whose Package
Document version attribute designates a version lower than "3.0" or which omits the version
attribute.
Forward Compatibility
›
It SHOULD attempt to process any given Rendition of an EPUB Publication whose Package
Document version attribute designates a version higher than "3.0".
XML Processing
›
It MUST be a conformant non-validating processor [XML].
›
It MUST be a conformant processor as defined in [XMLNS].
›
It MUST support xml-stylesheet processing instructions [ASSOCSS], and MAY support
additional processing instructions.
›
It MUST be a conformant application as defined by [XML Base].
NOTE
A conforming Reading System is not necessarily a single dedicated program or device, but
may exist as a distributed system.
› 3 Package Documents
› 3.1 Introduction
This section is informative
The Package Document carries bibliographic and structural metadata about a Rendition of an EPUB
Publication, and is thus the primary source of information about how to process and display that
Rendition.
The Package Document is an XML document consisting of a set of container elements, each
dedicated to housing information about a particular aspect of the Rendition. These containers
effectively centralize metadata, detail the individual resources that compose the Rendition and
10 © ISO/IEC 2020 – All rights reserved

provide reading order and other information for rendering the EPUB Publication is represents to a
User.
The following list summarizes the information a Package Document contains:
Rendition metadata — mechanisms for including and/or referencing metadata applicable to the
EPUB Publication and/or the specific Rendition of it, including for particular resources within the
Rendition.
A manifest — identifies (via IRI) and describes (via MIME media type) the set of resources that
collectively compose the given Rendition of the EPUB Publication.
A spine — an ordered sequence of ID references to top-level resources in the manifest from
which all other resources in the set can be reached or utilized. The spine defines the default
reading order of the given Rendition.
Fallback chains — an optional means for defining an ordered list of top-level resources that can
be considered content equivalents that a Reading System can choose between for rendering.
Bindings — an optional means of associating script-based implementations with custom media
types.
› 3.2 Content Conformance
A Package Document MUST meet all of the following criteria:
Document Properties
›
It MUST meet the conformance constraints for XML documents defined in XML Conformance.
›
It MUST be valid to the Package Document schema, as defined in Appendix A, Package
Document Schema , and conform to all content conformance constraints expressed in Package
Document Definition.
File Properties
›
The Package Document filename SHOULD use the file extension .opf.
Package Documents have the MIME media type application/oebps-package+xml [RFC4839].
› 3.3 Reading System Conformance
An EPUB Reading System MUST meet all of the following criteria:
Processing
›
It MUST process the Package Document in conformance with all Reading System conformance
constraints expressed in Package Document Definition.
›
It SHOULD process presentational metadata, as expressed in General Properties
›
It MUST process fixed layout metadata, as expressed in Fixed-Layout Properties
© ISO/IEC 2020 – All rights reserved 11

ISO/IEC 23736-1:2020(E)
›
For fixed layouts expressed using the rendition:layout property, it MUST determine the
rendering dimensions as defined in Fixed-Layout Documents [ContentDocs301] .
›
It MUST ignore proprietary metadata properties that pertain to layout expressions if they conflict
behaviorally with the property semantics defined in Fixed-Layout Properties.
› 3.4 Package Document Definition
All elements [XML] defined in this section are in the http://www.idpf.org/2007/opf namespace
[XMLNS] unless otherwise specified.
› 3.4.1 The package Element
The package element is the root container of the Package Document and encapsulates metadata and
resource information for a Rendition.
Element Name
package
Usage
The package element is the root element of the Package Document.
Attributes
version [required]
Specifies the EPUB specification version to which the given Rendition conforms.
The attribute MUST have the value 3.0 to indicate compliance with this version of the
specification.
unique-identifier [required]
An IDREF [XML] that identifies the dc:identifier element that provides the
package's preferred, or primary, identifier.
Refer to Publication Identifiers for more information.
prefix [optional]
Declaration mechanism for prefixes not reserved by this specification.
Refer to The prefix Attribute for more information.
xml:lang [optional]
Specifies the language used in the contents and attribute values of the carrying
element and its descendants, as defined in section 2.12 Language Identification of
[XML].
dir [optional]
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Specifies the base text direction of the content and attribute values of the carrying
element and its descendants.
Inherent directionality specified using [Unicode] takes precedence over this attribute.
Allowed values are ltr (left-to-right) and rtl (right-to-left).
id [optional]
The ID [XML] of this element, which MUST be unique within the document scope.
Content Model
In this order: metadata [required], manifest [required], spine [required], guide
[optional/deprecated], bindings [optional], collection [0 or more]
› 3.4.2 The metadata Element
The metadata element encapsulates meta information for the given Rendition.
Element Name
metadata
Usage
Required first child of package .
Attributes
The metadata element has no attributes defined in this specification.
Content Model
In any order: dc:identifier [1 or more], dc:title [1 or more], dc:language [1 or
more], DCMES Optional Elements [0 or more], meta [1 or more], OPF2 meta [0 or more],
link [0 or more]
The minimal required metadata that each Rendition of an EPUB Publication MUST include consists of
three elements from the Dublin Core Metadata Element Set [DCMES] — title , identifier and
language — together with the modified property from DCMI Metadata Terms [DCTERMS]. Refer to
the example at the end of this section for an instance of a complete minimal metadata set.
Additional optional metadata is expressed using the DCMES optional elements and the meta
element.
› Examples
The following example represents the minimal set of metadata that all Renditions have to contain.

…

© ISO/IEC 2020 – All rights reserved 13

ISO/IEC 23736-1:2020(E)
urn:uuid:A1B0D67E-2E81-4DF5-9E67-
A64CBE366809
Norwegian Wood
en
2011-01-01T12:00:00Z

…

› 3.4.3 The DCMES identifier Element
The [DCMES] identifier element contains a single identifier associated with the given Rendition of
the EPUB Publication, such as a UUID, DOI, ISBN or ISSN.
Element Name
dc:identifier
Namespace
http://purl.org/dc/elements/1.1/
Usage
Required child of metadata . Repeatable.
Attributes
id [optional]
The ID [XML] of this element, which MUST be unique within the document scope.
The id attribute is required on the identifier element containing the unique
identifier. See below.
Content Model
Text
Every Rendition's metadata section MUST include at least one identifier element containing an
unambiguous identifier for the EPUB Publication. Multiple identifier elements are permitted, but
only one can be marked as the Unique Identifier via the package element unique-identifier attribute.
The following example shows the unique identifier element for an EPUB Publication.


urn:uuid:A1B0D67E-2E81-4DF5-9E67-
A64CBE366809
…


14 © ISO/IEC 2020 – All rights reserved

This specification makes a distinction between the Unique Identifier for an EPUB Publication and the
identifier that uniquely identifies a specific version of it (i.e., to be able to differentiate different
versions of the same EPUB Publication). Whenever a Rendition is modified, it MUST include a new last
modified date.
To identify a specific version of a packaged EPUB Publication, a Release Identifier can be
constructed by combining the Unique Identifier with the last modified date of the Rendition. For more
information on the semantics and requirements of the Release Identifier, refer to Release Identifier.
Identifiers MAY differ from Rendition to Rendition.
This specification imposes no additional restrictions or requirements on identifiers except that they
MUST be at least one character in length. It is strongly RECOMMENDED that all identifiers be fully qualified
URIs, however.
Reading Systems MUST trim all leading and trailing whitespace from the element value, as defined by
the XML specification [XML], before processing the value.
To determine whether an identifier conforms to an established system or has been granted by an
issuing authority, Reading Systems SHOULD parse the value of the property. For additional precision
(e.g., if the scheme cannot be determined from the value or could lead to an ambiguous result),
Authors MAY attach an identifier-type property to assist in Reading System identification. When
included, the identifier-type property SHOULD take precedence over value parsing the identifier.
The following example shows how an identifier can be additionally marked as a DOI using the
identifier-type property.

urn:doi:10.1016/j.iheduc.2008.03.001
scheme="onix:codelist5">06
…

This specification does not require or endorse the use of any specific scheme for identifiers, and
imposes no restrictions or requirements on identifier-type identifiers beyond those specified in the
property definition.
When an EPUB Publication is derived from another publication, the identifier for that source
publication MAY be included in the EPUB Publication metadata, and MUST be represented using the
DCMES source element.
› 3.4.4 The DCMES title Element
The [DCMES] title element represents an instance of a name given to the EPUB Publication.
Element Name
dc:title
Namespace
http://purl.org/dc/elements/1.1/
© ISO/IEC 2020 – All rights reserved 15

ISO/IEC 23736-1:2020(E)
Usage
Required child of metadata . Repeatable.
Attributes
id [optional]
The ID [XML] of this element, which MUST be unique within the document scope.
xml:lang [optional]
Specifies the language used in the contents and attribute values of the carrying
element and its descendants, as defined in section 2.12 Language Identification of
[XML].
dir [optional]
Specifies the base text direction of the content and attribute values of the carrying
element and its descendants.
Inherent directionality specified using [Unicode] takes precedence over this attribute.
Allowed values are ltr (left-to-right) and rtl (right-to-left).
Content Model
Text
Every metadata section MUST include at least one title element containing the title for the EPUB
Publication. Multiple title elements are permitted, but the title-type property SHOULD be attached
to indicate the type of title (e.g., the main title of a work or a subtitle).
The following example shows how to indicate different title types.

…
A Dictionary of Modern English Usage
main

First Edition
edition

Fowler's
short
…

When adding the title-type property, Authors SHOULD designate only one title element as
containing the main title for the Publication. If no means of determining title types is provided, or
understood, Reading Systems MUST treat the first title element in document order as the main title.
This specification does not define how additional title elements SHOULD be processed in such
situations.
16 © ISO/IEC 2020 – All rights reserved

The optional display-seq property MAY also be attached to each title to indicate their primacy for
display and other rendering purposes.
The following example shows how to indicate display sequence.

…
The Red and the Black
main
1

A Chronicle of the Nineteenth Century
subtitle
2

A Chronicle of 1830
subtitle
3
…

Titles MAY differ from Rendition to Rendition.
This specification imposes no additional restrictions or requirements on titles except that they MUST be
at least one character in length.
Reading Systems MUST trim all leading and trailing whitespace from the element value, as defined by
the XML specification [XML], before processing the value.
› Examples
The following example shows how the title "THE LORD OF THE RINGS, Part One: The Fellowship of the
Ring" could be classified.

The Fellowship of the Ring
main

The Lord of the Rings
collection

THE LORD OF THE RINGS, Part One: The Fellowship of
the Ring
expanded
…

The following example shows how the complex title "The Great Cookbooks of the World: Mon premier
guide de cuisson, un Mémoire. The New French Cuisine Masters, Volume Two. Special Anniversary
Edition" could be classified.

Mon premier guide de cuisson, un
Mémoire
main
© ISO/IEC 2020 – All rights reserved 17

ISO/IEC 23736-1:2020(E)
2

The Great Cookbooks of the World
collection
1

The New French Cuisine Masters
collection
3

Special Anniversary Edition
edition
4

The Great Cookbooks of the World:
Mon premier guide de cuisson, un Mémoire.
The New French Cuisine Masters, Volume Two.
Special Anniversary Edition
expanded
…

› 3.4.5 The DCMES language Element
The [DCMES] language element specifies the language of the content of the given Rendition.
Element Name
dc:language
Namespace
http://purl.org/dc/elements/1.1/
Usage
Required child of metadata .
Attributes
id [optional]
The ID [XML] of this element, which MUST be unique within the document scope.
Content Model
Text
Each Rendition's metadata section MUST include at least one language element with a value
conforming to [RFC5646].
The following example shows an EPUB Publication is in U.S. English.
18 © ISO/IEC 2020 – All rights reserved


…
en-US
…

Additional language elements MAY be included for multilingual Publications, but each element's value
MUST conform to [RFC5646].
Languages MAY differ from Rendition to Rendition.
Reading Systems MUST trim all leading and trailing whitespace from the element value, as defined by
the XML specification [XML], before processing the value.
› 3.4.6 The DCMES Optional Elements
All elements from the [DCMES] element set — except for identifier , language and title , as
defined above — are designated as optional. These elements all conform to the following generalized
definition:
Element Name
contributor | coverage | creator | date | description | format | publisher | relation |
rights | source | subject | type
Namespace
http://purl.org/dc/elements/1.1/
Usage
Optional child of metadata . Repeatable.
Attributes
id [optional]
The ID [XML] of this element, which MUST be unique within the document scope.
xml:lang* [optional]
Specifies the language used in the contents and attribute values of the carrying
element and its descendants, as defined in section 2.12 Language Identification of
[XML].
dir* [optional]
Specifies the base text direction of the content and attribute values of the carrying
element and its descendants.
Inherent directionality specified using [Unicode] takes precedence over this attribute.
Allowed values are ltr (left-to-right) and rtl (right-to-left).
© ISO/IEC 2020 – All rights reserved 19

ISO/IEC 23736-1:2020(E)
Content Model
Text
* The xml:lang and dir attributes are permitted only on the following elements: contributor,
coverage, creator, description, publisher, relation, rights and subject.
Optional metadata MAY differ from Rendition to Rendition.
The value of all optional [DCMES] elements MUST be at least one character in length.
Reading Systems MUST trim all leading and trailing whitespace from the element value, as defined by
the XML specification [XML], before processing the value.
Except as detailed below, this specification does not modify the [DCMES] definitions for these
elements.
› The DCMES contributor Element
The contributor element is used to represent the name of a person, organization, etc. that played a
secondary role in the creation of the content of an EPUB Publication.
The use of the contributor element is identical to the use of the creator element in all other
respects, as detailed in the next section.
› The DCMES creator Element
The creator element represents the name of a person, organization, etc. responsible for the creation
of the content of an EPUB Publication. The role property can be attached to the element to indicate
the function the creator played in the creation of the content.
The following example shows how to represent a creator as an author using a MARC relators term.

…
Haruki Murakami
id="role">aut
…

The creator element SHOULD contain the name of the creator as a Reading System will present it to a
User. The file-as property MAY be attached to include a normalized form of the name, and the
alternate-script property can be used to represent a creator's name in another language or script.
The following example shows the different ways a creator's name can be included to facilitate processing
and rendering.

…
Haruki Murakami
id="role">aut
20 © ISO/IEC 2020 – All rights reserved

村
上 春樹
Murakami, Haruki
…

If an EPUB Publication has more than one creator, each SHOULD be included in a separate creator
element. The order in which to render the creator names SHOULD be specified using the display-seq
property.
The following example shows how to indicate the display order for creator elements.

…
Lewis Carroll
scheme="marc:relators">aut
1

John Tenniel
scheme="marc:relators">ill
2
…

If no means of establishing the primacy of creators for rendering is identifiable, Reading Systems
MUST use the document order of creator elements in the metadata section (i.e., where the first creator
element encountered is the primary creator). If a Reading System exposes creator metadata for the
User, it SHOULD include all the creators listed in the metadata section whenever possible (e.g., when
not constrained by display considerations).
Secondary contributors SHOULD be represented using DCMES contributor elements.
› The DCMES date Element
The date element MUST only be used to define the publication date of the EPUB Publication. The
publication date is not the same as the last modified date (the last time the Rendition was changed),
which MUST be included using the [DCTERMS] modified property.
It is RECOMMENDED that the date string conform to [ISO8601], particularly the subset expressed in W3C
Date and Time Formats [DateTime], as such strings are both human and machine readable.
...