What are the big changes with EPUB 3.1 and what do they mean?

15 June 2017

AZARDI, ePub, ePub3.1, IDPF, e-Books, EPUB3.1 Samples.

A few comments and observations on the new EPUB 3.1 specification released by the IDPF in February 2017.

Looking at the changes

The changes from previous ePub versions are potentially important for Education Publishers who are considering EPUB as a learning content delivery option. Especially if they are looking for more interactivity. For standard tradebook  publishers the EPUB 3.1 changes are of little of consequence.

We have listed the changes from ePub 3.0.1 and EPUB 3.1 below and commented on how this affects the AZARDI EPUB reader and the impact for publishers.


"The opposite of every truth is just as true. Everything is one-sided which can be thought with thoughts and said with words.

Hermann Hesse. Siddartha

The Changes

Most of the significant changes happened because the W3C insisted on full W3C specification compliance for the Content Document spec.

The digital content delivery world has changed wildly since 2011 as we watch the concept of an "application" transform to WebApps it was essential to catch up with the massive advances of the mobile/Internet.  Most of the EPUB spec. changes are simple pragmatic decisions. But of course the IDPF is still trying to keep the packaging complex and confusing.

Let's Look At EPUB 3.1!

Below is the IDPF's specification difference list. For simplicity this is ordered and numbered to match the EPUB 3.1 Changes document.

The most interesting changes are in Content Documents 3.1. where the power of the W3C specifications has at last been unshackled from the myopic vision of a digital book being some sort of imitation print book. While that has some value for fiction, it has no value for education and other new content engagement experiences.

About the Number Links

The numbers with the arrows link directly to the related IDPF document section. Some items have been left out as they are just re-writes or clarifications and there is nothing to comment.

About the Red Bar

The list of items with the red bar down the side are EPUB packaging changes which don't particularly affect e-book production. They just make packaging an EPUB more or less complex. IGP:Digital Publisher does that packaging without any publisher work overhead so the changes don't affect .

2 Specification Reorganization

This is a non-issue. The new documents do seem a bit more "linky". It takes a bit of time to learn and if they didn't have the changes document it would be hell working out what an EPUB 3.1 introduces.

3. EPUB 3.1 General Statements

3.1 Accessibility Support.

This is a given and full compliance with the W3C standards is strongly recommended.

3.2 New Core Media Types.

WOFF2 and SFNT fonts are added. No shocks here as WOFF2 is a W3C standard and other SFNT fonts such as TrueType (TTF), OpenType (OTF and OpenFontFormat (OFF) have been the backbone of the Internet forever and all use the SFNT table packaging.

3.4 Remotely Hosted Resources

Audio, video scripts and fonts can now officially be located outside the EPUB Container. We have been doing this for years already as it makes delivery of 10s of thousands of EPUBs to students or other users faster and easier. As a catch this is an optional feature for Reading systems.

3.5 Removed EPUBCFI Support

Canonical Fragment Identifiers (CFI) are no longer required to be supported by a Reading System. We made that decision back in 2011 and so did every other reading system on the planet. It remains a part of the spec.

4 Packages 3.1

This section lists deprecated and removed elements and attributes. No shocks here. It's both a clean up and new trap section with exciting new useless

Deprecated: refines attribute (and a lot of replacements added) and the old ePub 2 NCX (Navigation Center). AZARDI will continue to be NCX aware as it has to be able to open and display all versions of EPUB. That is a ground reality.

Removed: the OPF2 <meta>, <guide>and <bindings> elements.

5 Content Documents 3.1

This is where the changes get interesting and important for publishers and content creators. EPUB content is free again!

5.1 Support for HTML Syntax of HTML5

It's full HTML5/XHTML5 without locked back version numbers. The most important item is that EPUB content can now keep up with W3C changes and new features. That means the same content you use to package into EPUBs can be used in WebApps and Online as well. Of course with IGP:Digital Publisher it can also be processed as PDFs for print.

5.2 Replacement of ePub Style Sheets with CSS References

No CSS restrictions. Yay! In five or six years ePubCheck 11 wont reject our essential absolute or fixed CSS positioning properties in textbooks.

This slightly crazy restriction was originally put in place because of Reading systems artifical paging clashed when it was used. Instead of sorting out reading systems of CSS was crushed.

EPUB 3.1 also dumps a load of -epub- prefixed CSS properties. Excellent. More arbitrary "standard" into the bin.

Education publishers in particular have to ensure they select the right reading systems like AZARDI to ensure they can use fixed and absolute layout for presentation of concepts and exercises, etc..

5.3 Prioritization of Author and User Styles

We don't have anything to do here. AZARDI reading systems have always prioritized the presentation styling of the book. This was our Fifth Guiding Principle - Content Neutrality, published in 2012.

This is very important for highly interactive education and training content of course. A reading system MUST preseent the authors intentions.

5.4 Scripting Support Clarifications

This is a real-world catch-up. AZARDI has incredibly powerful rendition:flow properties and can assert them on a section by section basis. Most reading systems provide a book imitation lock-in.

5.5 Removal of the Switch Element

AZARDI never supported this. Now we don't need to think about the switch element. Just use standard HTML alternative properties.

5.6 Removal of the Trigger Element

AZARDI never supported this and we rejected this as a silly feature in 2012.  Now we get to officially use the HTML audio and video elements, which of course are all that have been realistically usable for five years. Excellent.

 So now EPUB 3.1 is fully W3C specification compliant the quicker publishers move to this the better.

7 Media Overlays

No shocks here.

8 EPUB Accessibility

A full specification and guidelines are now provided. Because of the IGP:FoundationXHTML semantics, using the ARIA role=" " attribute and the epub:type attribute remain very straight-forward. We will discuss this and how it is being handled in IGP:Digital Publisher and AZARDI Readers in a separate article.

Summarizing it all

With assimilation into the larger W3C the IDPF have to "play the real standards game". That has happened instantly with HTML, CSS, SVG and Javascript in Content Documents.

Another upside is that for new features the W3C rule is there must be two implementations. We would be interested in that for sensible and valuable features. The great thing is the W3C have forced the IDPF to put their feet a little closer to Planet Earth.

There are other outstanding issues such as why have <spine> and <nav> when they are pretty much the same as we explored with EBOOK ZERO back in 2013.

Since 2007 we have had to take the IDPF "specifications" the 1990's focused "IDPF crew" writes, with no implementation, no testing, no market engagement; and turn it into something practical and real for production, distribution and user engagement. We have led the pack. We reluctantly continue to do so with EPUB 3.1 production systems and Readers.

IGP are digital content practioners creating production, delivery and reading solutions for publishers around the world in dozens of languages.

We maintain hundreds of thousands of books and documents for publishers around the world in IGP:Digital Publisher tagged with IGP:FoundationXHTML. All of these books, even those created as early as 2008 will be able to be instantly processed to EPUB 3.1 or any other format if and when required. And that is important in this fast changing digital age.

Digitize Once. Use Forever.

Posted by Richard Pipe

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