EPUB 3.0.1 Changes from EPUB 3.0

Draft Specification 8 November 2013

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Markus Gylling, International Digital Publishing Forum (IDPF)

Matt Garrish, Invited Expert

Table of Contents

1. Introduction
1.1. EPUB Revision History
2. EPUB Publications
2.1. The spine element
2.2. The dc:source element
2.3. The dc:type element
2.4. The collection element
2.5. Reserved prefixes
2.6. Collections metadata
2.7. Link relationships
2.8. The record property
2.9. Fixed-layout metadata
2.10. The rendition:flow property
2.11. The rendition:align-x-center property
3. EPUB Content Documents
3.1. Reserved prefixes
3.2. Semantic Enrichment
3.3. The trigger element
3.4. Custom Attributes
3.5. The aria-describedat attribute
3.6. New CSS 3 modules
3.7. CSS Writing Modes
3.8. The oeb-page-head and oeb-page-foot properties
3.9. RelaxNG schemas
4. EPUB Open Container Format (OCF)
4.1. Terminology
4.2. Obfuscation algorithm
5. EPUB Media Overlays
5.1. The playback-active-class property
6. Structural Semantics Vocabulary
A. Acknowledgements and Contributors

 1 Introduction

EPUB® is an interchange and delivery format for digital publications, based on XML and Web Standards. An EPUB Publication can be thought of as a reliable packaging of Web content that represents a digital book, magazine, or other type of publication, and that can be distributed for online and offline consumption.

This document, EPUB 3.0.1 Changes from EPUB 3.0, describes changes made in the first minor revision of the EPUB 3.0 specifications, highlighting key changes and additions.

This document is non-normative. Consult the EPUB specification documents for definitive information on EPUB 3:

  • EPUB Publications 3.0.1 [Publications301], which defines publication-level semantics and overarching conformance requirements for EPUB Publications.

  • 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) Container.

  • EPUB Media Overlays 3.0.1 [MediaOverlays301], which defines a format and a processing model for synchronization of text and audio.

Unless otherwise specified, terms used herein have the meaning defined in these specifications.

 1.1 EPUB Revision History

EPUB had its roots in the interchange format known as the Open EBook Publication Structure (OEBPS). OEBPS 1.0 was approved in 1999 by the Open eBook Forum, an organization that later became the International Digital Publishing Forum (IDPF). Subsequent revisions 1.1 and 1.2 were approved by the IDPF in 2001 and 2002 respectively.

It was realized that a need existed for a format standard that could be used for delivery as well as interchange, and work began in late 2005 on a single-file container format for OEPBS, which was approved by the IDPF as the OEBPS Container Format (OCF) in 2006. Work on a 2.0 revision of OEBPS began in parallel which was approved as the renamed EPUB 2.0 in October, 2007, consisting of a triumvirate of specifications: Open Package Format (OPF), Open Publication Format (OPF) together with OCF. EPUB 2.0.1, a maintenance update to the 2.0 specification set primarily intended clarify and correct errata in the specifications, was approved in September, 2010. [OPF2] [OPS2] [OCF2]

Work on a major new 3.0 revision of the EPUB specifications began in 2010, with the goal of aligning EPUB more closely with HTML5, and in the process bringing new, native multimedia features, sophisticated CSS layout rendering and font embedding, scripted interactivity, enhanced global language support, and improved accessibility. A new specification, EPUB Media Overlays was also introduced, enabling text and audio synchronization in EPUB Publications. To better align the specification names with the standard, the Open Package Format specification was renamed EPUB Publications and the Open Publication Format specification was renamed EPUB Content Documents. The EPUB 3.0 specifications were approved in October, 2011. [Publications30] [ContentDocs30] [OCF30] [MediaOverlays30]

 2 EPUB Publications

 2.1 The spine element

All Content Documents referenced from Content Documents in the spine [Publications301] now themselves have to be listed in the in the spine.

 2.2 The dc:source element

The restriction to only one dc:source element [Publications301] has been removed.

Identification of the print source for pagination is now done by refining the dc:source element with the new source-of property [Publications301] .

 2.3 The dc:type element

The restriction to only one dc:type element [Publications301] has been removed.

Refer to the EPUB Registry of Publication Types for the list of IDPF-recognized types that can be used with this element.

 2.4 The collection element

The new collection element [Publications301] provides a framework for developing specialized behaviors and rendering in EPUB 3. It is not intended for use as defined in the Publications specification by Authors, but provides an extension point for functionality to be built on top of. It is being used by the EPUB Indexes specification, for example, to allow an index split across multiple XHTML Content Documents to be identified and rejoined (e.g., for machine processing and presentation).

 2.5 Reserved prefixes

The list of reserved prefixes that can be used in package metadata has been removed from the Publications specification to simplify adding prefixes outside of a specification revision. The list of prefixes can now be found in EPUB Publications Reserved Prefixes.

The prefix sch has been reserved for including schema.org metadata.

 2.6 Collections metadata

The meta element metadata properties have been expanded to allow the collection an EPUB Publication belongs to to be identified. The belongs-to-collection property [Publications301] identifies the collection title and the collection-type [Publications301] the nature of the collection (series and sets are predefined values).

 2.8 The record property

A new generic record property has been added for the link element, allowing the referencing of any metadata record that can be identified by its media type.

 2.9 Fixed-layout metadata

Fixed-layout metadata that was formerly defined in EPUB 3 Fixed-Layout Documents has now been merged into the [Publications301] and [ContentDocs301] specifications. All of the fixed-layout metadata properties [Publications301] are now defined in Publications, and support for these properties is now required in Reading Systems.

 2.10 The rendition:flow property

The rendition:flow property [Publications301] was added to allow Authors to indicate the desired way in which to flow Content Documents (e.g., to create a continuous flow).

 2.11 The rendition:align-x-center property

The rendition:align-x-center property [Publications301] was added to enable Authors to specify that Content Documents are to be centered horizontally. This property was added primarily to handle the problem of Naka-Tobira.

 3 EPUB Content Documents

 3.1 Reserved prefixes

The list of reserved prefixes that can be used in epub:type attribute has been removed from the Content Documents specification to simplify adding prefixes outside of a specification revision. The list of prefixes can now be found in EPUB Content Documents Reserved Prefixes.

 3.2 Semantic Enrichment

Both [RDFa11] and [Microdata] attributes are now valid for use in XHTML Content Documents. Vocabularies, such as defined at schema.org, can be used with these attributes to enrich content.

 3.3 The trigger element

The following [XML Events] have been added to the trigger element [ContentDocs301] to override default behaviors and prevent propagation of events: phase, defaultAction and propagate.

 3.4 Custom Attributes

Custom attributes [ContentDocs301] are now allowed in XHTML Content Documents.

To improve interoperability, the IDPF is maintaining a registry of custom attributes.

(Note that custom attributes have always been allowed in SVG provided they meet the requirements outlined in that specification.)

 3.5 The aria-describedat attribute

The new [WAI-ARIA-1.1] aria-describedat attribute [ContentDocs301] has been added, allowing out-of-band descriptions to be added to any element. Descriptions referenced from this attribute can be located inside or outside the EPUB Container.

 3.6 New CSS 3 modules

Two new modules have been added to the baseline profile:

 3.7 CSS Writing Modes

The syntax and values of the CSS Writing Modes properties have changed. Refer to CSS Writing Modes [ContentDocs301] for more information.

 3.8 The oeb-page-head and oeb-page-foot properties

The use of the oeb-page-head and oeb-page-foot properties [ContentDocs301] is now deprecated, as these properties are expected to be removed or replaced in a future revision.

 3.9 RelaxNG schemas

The Content Documents specification no longer references snapshots of the externally maintained [HTML5] and [SVG] schemas. The schemas have been decoupled so that validation can be kept current with changes to those specifications (primarily HTML5).

 4 EPUB Open Container Format (OCF)

 4.1 Terminology

The nature of the contents of an OCF Container has been clarified: an EPUB Publication is now defined as the single work represented in the Container, and is represented by one or more Renditions of its content (previously each Rendition was defined as an EPUB Publication, even though the Renditions could all be related).

It is no longer valid for Renditions of different EPUB Publications to be bundled together, although this was not encouraged previously.

 4.2 Obfuscation algorithm

The order of obfuscation and compression of resources has been clarified in Obfuscation Algorithm [OCF301] such that obfuscation is required to occur before compression. Reading System developers are advised to consider that the reverse order may be encountered due to the lack of clarity previously (see the note at the end of the section for more information).

 5 EPUB Media Overlays

 5.1 The playback-active-class property

The addition of the playback-active-class property allows Authors to control the appearance of text that is not currently being read. This property is applied to a Content Document's document element (e.g., the [HTML5] html element). The property could be used to grey out all text when playback is active, for example, to better focus the User's attention on the text that is currently being read.

 6 Structural Semantics Vocabulary

Updating the EPUB Structural Semantics Vocabulary has been unbound from the EPUB specifications revision cycle. The EPUB Working Group can now vet new property requests and make additions on an ongoing basis.

Many new additions were made to the vocabulary, most notably a new section dedicated to educational properties. Refer to the EPUB wiki for a complete list of changes.

 Appendix A. Acknowledgements and Contributors

This appendix is informative

EPUB has been developed by the International Digital Publishing Forum in a cooperative effort, bringing together publishers, vendors, software developers, and experts in the relevant standards.

The EPUB 3 specifications were prepared by the International Digital Publishing Forum’s EPUB Maintenance Working Group, operating under a charter approved by the membership in May, 2010 under the leadership of:

Active members of the working group included:

 IDPF Members

 Invited Experts/Observers

For more detailed acknowledgements and information about contributors to each version of EPUB, refer to Acknowledgements and Contributors [EPUB3Overview] .


Normative References

[ContentDocs30] EPUB Content Documents 3.0 .

[ContentDocs301] EPUB Content Documents 3.0.1 .

[MediaOverlays30] EPUB Media Overlays 3.0 .

[MediaOverlays301] EPUB Media Overlays 3.0.1 .

[Microdata] HTML Microdata (20121025) . Ian Hickson. 25 October 2012.

[Publications30] EPUB Publications 3.0 .

[Publications301] EPUB Publications 3.0.1 .

[RDFa11] RDFa Core 1.1 - Second Edition . Syntax and processing rules for embedding RDF through attributes. Ben Adida, et al. 22 August 2013.

[SVG] Scalable Vector Graphics (SVG) 1.1 (Second Edition) . Erik Dahlström, et al. 09 June 2011.

[WAI-ARIA-1.1] Accessible Rich Internet Applications (WAI-ARIA) 1.1 . James Craig, et al.

[XML Events] XML Events . Shane McCarron, et al. 14 October 2003.

Informative References

[EPUB3Overview] EPUB 3 Overview . Garth Conboy, et al.