Ebooks file formats

Ebooks can come in different formats. For the purposes of our project, we focus on the two mainstream formats widely adopted worldwide: PDF and EPUB.

EPUB
(Electronic PUBlication) is an open file format for electronic publications. The first version, named OEBPS 1.0 (Open EBook Publication Structure) was approved in 1999 by the Open eBook Forum, which later became the International Digital Publishing Forum. EPUB 2.0 was released in 2010, followed in June 2014 by version 3, in which for the first time in the specifications were included accessibility features. Just after the release of EPUB 3.1 in January 2017, the IDPF merged into the W3C, making the EPUB an official W3C recommendation (standard). The last version, EPUB 3.3, was published on May 25, 2023.
EPUB is a native semantic format allowing to use numerous taggings from different standardised languages such as HTML, ARIA, MATHML, SVG and others. a distribution and interchange format for digital publications and documents. Provides a means of representing, packaging, and encoding structured and semantically enhanced Web content — including HTML, CSS, SVG and other resources — for distribution in a single‐file container. Specification created by IDPF - Industrial Digital Publishing Forum) and maintained by W3C (World Wide Web Consortium) since 2017.
PDF
Portable Document Format, created by Adobe in 1992 and standardised as an open standard, maintained by the International Organization for Standardization (ISO). The PDF ISO declines in special purposes such as PDF/A for archiving, PDF/E for engineering, and PDF/X for printing, PDF/UA for accessibility.
Initially purposed for print reliability and digital conservation, the format is based on PostScript, a computer language to geographically describe ressources (a point of that color must appear at this position). As it went to be used for digital consultation and evolved to respond as best as possible to this use principally with the addition of a semantic descriptive layer composed of XML language tags. The variety of tagging that can be added is currently limited to 28 elements. The PDF/UA ISO standard provides definitive terms and requirements for accessibility in PDF documents and applications.

Abbreviations

EAA
European Accessibility Act
ACE
Accessibility Checker for EPUB
EU
European Union
EPUB
Electronic Publication
FXL
Fixed Layout
FEP
Federation of European Publishers
KPI
Key Point Indicators
RFL
Reflowable
RGTK
Readium Go Tool Kit
PDF
Portable Document Format
WCAG
Web Content Accessibility Guidelines

Norms and Standards

The European Accessibility Act (EAA)
Annex I sections III and IV linea f).
EPUB Accessibility - EU Accessibility Act Mapping
https://www.w3.org/TR/epub-a11y-eaa-mapping/
EPUB Accessibility 1.1
https://www.w3.org/TR/epub-a11y-11/
WCAG 2.1 AA
https://www.w3.org/TR/WCAG21/
ONIX
The ONIX family includes standards for Books, Serials and Licensing Terms and rights Information. In this document, we use ONIX to refer to ONIX for Books. The ONIX for Books Product Information Message is the international standard for representing and communicating book industry product information in an
Thema
the subject category scheme for a global book trade version 1.5, EDItEUR, 2022. Available at https://ns.editeur.org/thema/en