The EPUB3 is one of the most accessible digital publishing formats. It is based on web technologies therefore, most of the accessibility guidelines and best practices of web development apply here too. This format is recommended for books, reference material, class handouts and other documents intended for reading-only.
- The EPUB format
- An EPUB publication is basically a self-contained website that holds the content of the publication and functionalities for enhanced navigation and discoverability.
- You may use EPUB editing tools like SIGIL by Sigil to explore the inner structure and source code of EPUBs.
- To better understand the accessibility issues and mitigation actions, it could be necessary to know about the inner structure of this format. This is well described on the page Anatomy of an EPUB 3 file by EDRLab.
- EPUBs contain a wide variety of elements and the accessibility has to be considered too. Some of them are:
- Images in PNG and other raster formats. See: Pictures and images.
- MathML. To know more about implementing accessible maths go: W3C Math Home by W3C.
- SVG. Learn more about accessible Scalable Vector Graphics at: SVG at the Working group on graphics by W3C.
- SMIL. To know more about Synchronized Multimedia Integration Language at Synchronized Multimedia by W3C.
- In the Supported Media Types - EPUB3 specification by W3C you may find all supported element types.
- Creation from an accessible document
The easiest way of creating an EPUB is from an accessible Word document and using the tool WordToEPUB by DAISY created by the DAISY Consortium. The main steps are:
- Start from an accessible Word document. To know more go to Accessible office documents.
- Use the WordToEPUB by DAISY.
- Use the advance option to:
- set the metadata,
- add extra content like maths formulas and
- Convert to PNG the images in incompatible formats. To know more go to: 3.1.2 Supported Media Types - EPUB3 specification.
- Automated accessibility checking
A good starting point for assessing the accessibility of digital documents is the use of automated accessibility checking tools. This detects accessibility problems that can be checked programmatically, reducing the workload. Then, the user has to focus only on the accessibility issues that an automatic checker cannot find.
One free and open source tool that you can use is Ace by DAISY Consortium. There is a Ace FAQ page by DAISY Consortium where you may find instructions for installing and using it.
- Manual accessibility checking
- Tere is an introductory and non-complete list of manual checks to assure the accessibility of EPUB publications.
- There is a cover page.
- Table of content is accessible and users can use it to jump directly to specific sections and pages. More at: 3.4.1 Page navigation by W3C in the EPUB Accessibility 1.1 specification.
- Review the metadata and assure that the information is accurate and correct in the file META-INF/metadata.xml.
- Language (dc:language by W3C). This takes the language identifiers defined in the XML specification by W3C.
- Title (dc:title by W3C).
- Author (dc:creator by W3C).
- Description (dc:description).
- Publisher (dc:publisher).
- ISBN (if any) (dc:identifier by W3C id="isbn"). E.g. <dc:identifier id="isbn">ISBN: 978-1449329143</dc:identifier>
- Date of publication (dc:date).
- Rights (dc:rights). Licence of the content. E.g. Creative Commons by Creative Commons.
- Subject (dc:subject by W3C). It should describe the topics covered by the publication.
- Check that the logical reading order matches with the physical one.
- Use keyboard-only to verify that it is possible to navigate through the whole document without the need of pointing devices.
- The alternative texts of the non-textual elements accurately describe the information they contain.
- Use assistive technology with the EPUB document to check that the information is properly displayed.
- Check other accessibility issues to assure the HTML and CSS comply with Web Content Accessibility Guidelines (WCAG) 2.0. See: Web.