EPUB is no portable website

EPUB is a book (L’EPUB est un livre). EPUB is not a book (L’EPUB n’est pas un livre). Any case, it is no codex, which is so obvious that we have to proceed further…


The W3C November 2013 Highlights underlines that there are some differences between the web world and the publishing world, even though both lean on common so-called technologies: (X)HTML, CSS, DTD to name a few at the very core.

The publishing industry is always an early adopter of Web technology. Recently, they built EPUB 3.0, the latest version of that standard from the International Digital Publishing Forum (IDPF), around a foundation of HTML, CSS, and SVG. Through our outreach to IDPF and other leading consortia in the publishing industry, including BISG, EDitEUR, IPTC, the Daisy Consortium, and NISO we know that W3C standards may not yet provide all the necessary features for digital publishers.

For publishing, fonts, typography, fine-tuned layout (even in a reflowable mode) are key.

Fonts are dear to publishers and we have good font news from the past six months. CSS Fonts Module Level 3, which advanced to Candidate Recommendation in October, brings to typography on the Web what was already possible in print: detailed control of advanced font features. Together with WOFF fonts, designers can use OpenType features such as « tabular figures » in financial tables or decorative « swash forms » typically used at the start or end of a word. Meanwhile, the Web Fonts Working Group is approaching a First Public Working Draft for WOFF 2.

Of course, not all publishers are good at typography. Of course, EPUB isn’t the sole format but the strive for openness is valuable as such. Of course, any discourse of that ilk blends strategy and claim pro domo. So what? Let’s take as it is, because those consortiums are key players setting standards, hence future usage/issues/actors reconfiguration.

EPUB in short

To date, one of the best resources to grasp the evolution of E-Publication is the EPUB 3 Best Practices published by O’Reilly Media in last January. This (e)book goes beyond the mere presentation of the new capabilities.

One of the most common misconceptions about EPUB is that it is a “flavor” of XML. (“Should I use EPUB or DocBook?” or, even worse, “Should I use EPUB or HTML5?” Hint: EPUB (pretty much) = HTML5.) Due partly to the convenient single-file format provided as .epub, people sometimes fail to realize that EPUB is not just, and not mainly, a specification for the markup of content documents. It is a publication format, and as such it specifies and documents a host of things that publications need to include—content documents, style sheets, images, media, scripts, fonts, and more, as discussed in detail in the other chapters of this book. In fact, EPUB is sometimes thought of as “a website in a box,” though it is actually much more than that.

What is arguably the most important thing about it is this: it organizes all the stuff in the box. It’s designed to enable reading systems to easily and reliably know, up front, what’s contained in a given publication, where to find each thing, what to do with it, how the parts relate to each other. And it enables publishers to provide that information in one clear, consistent form that all reading systems should understand, rather than in different, proprietary ways for each recipient system.

This, of course, is what metadata is for: it’s not the content, it’s information about the content. EPUB 3 accommodates much richer metadata than EPUB 2 did, and it enables that metadata to be associated not just with the publication as a whole, but also with individual components of the publication and even with elements within the content documents themselves. While it doesn’t require much more than EPUB 2 did (in the interest of backward compatibility), it accommodates the much richer metadata that makes publications so much more discoverable and dynamic, so much more usable and useful.

The place where all this information is organized is the package document, an XML file that is one of the fundamental components of an EPUB, the .opf file. (The extension .opf stands for Open Package Format, which was the precursor to the new Publications specification.) In addition to containing most of the EPUB’s metadata, the package document serves as a hub that associates that metadata with the other resources comprising the EPUB. All of this is then literally “zipped up” in a single-file container, the .epub file. Voilá, the “website in a box”—but one with a complete packing list and indispensable assembly instructions that ensure that an EPUB 3–compliant reading system will deliver the publication properly to the end user.

An ecosystem hybridises technologies obviously, along with actors (human and non-human, that said in a Latourian perspective), with value (proposition, and much more), with standards/rules. Let’s write this hypothesis: the web one is more focused on immediate combination of a variety of media; the publishing one is keener on long-term accessibility (hence, XML, greater emphasis on the separation of styles). There should be no surprise that even though W3C have been building the ground work for web ever since 1994, not long after the HTML advent, IDPF (International Digital Publishing Forum) works on the publishing challenges to build up the (open) standards for EPUB.

The issue is not here, not yet, to consider whether EPUB is the best foreseen solution, but to take into consideration that it exists and expands. Web vs. EPUB? Virginie Classen has just released (in french) her comment: EPUB, commenter la leçon (TeXtes), why EPUB is a good solution, from a publisher perspective. She replies to Nicolas Morin’s About the epub mantra (Medium).


Well, this is all the more raw not to restrain from calling for further consideration. The aforementioned O’Reilly book is so rich that this post, this blog DigitEditLab and presumably this project might elaborate on it. Hence, more to come anyhow.

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