EPUB Accessibility Techniques 1.1

4.1.1 Helpful Resources

EPUB Creators not familiar with the [WCAG2] may find the number of techniques daunting, as they are intended to provide broad coverage of possible solutions.

Assistance applying these techniques to EPUB Content Documents is available from the following sources:

• DAISY Accessible Publishing Knowledge Base — compendium of best practices by content type, with links to the applicable WCAG techniques.

• BISG Quickstart Guide to Accessible Publishing — includes a set of top practices for making content accessible.

4.2.1 ACCESS-001: Ensure meaningful order of content across spreads

[WCAG2] Success Criterion 1.3.2 specifies that each Web page have a meaningful order (i.e., that the visual presentation of the content match the underlying markup).

As EPUB allows two documents to be rendered together in a synthetic spread [EPUB-3], the order of content within a single document cannot always be evaluated in isolation. Content may span visually from one document to the next. For example, a sidebar might span the bottom of two pages.

Ordering each document separately by the visual display will lead to users of assistive technologies encountering gaps between the start and end of the spanned text. If the markup cannot be arranged to provide a more logical reading experience (e.g., the beginning of the spanned content at the end of the first page followed by the conclusion at the start of the next), another means of satisfying this criteria will be necessary to avoid failure (e.g., a hyperlink could be provided to allow a user to jump from the break point on the first page to the continuation on the next).

4.2.2 ACCESS-002: Provide multiple ways to access the content

[WCAG2] Success Criterion 2.4.5 requires there be more than one way to locate a Web page within a set of Web pages. By default, EPUB Publications meet this WCAG requirement so long as EPUB Creators follow the EPUB requirements to include all EPUB Content Documents in the spine and ensure access to all non-linear documents [EPUB-3].

The reason an EPUB Publication passes by meeting these requirements has to do with differences in how a user interacts with the set of documents in an EPUB Publication. In particular, although an EPUB Publication typically consists of many Content Documents, Reading Systems automatically provide the ability for the user to move seamlessly from one document to the next, so long as they are listed in the spine [EPUB-3]. To the user, an EPUB Publication is a single document they have complete access to, not a set of disconnected pages that they need links to move through.

The required table of contents provides a second method to access the major headings of the publication. The user can jump to any heading and continue to navigate from there, regardless of how the publication is chunked.

Following these two requirements therefore satisfies the need for multiple ways to access the content. Reading Systems also typically provide search capabilities, something the EPUB Creator cannot provide, so users also have a third option available in most cases.

Although EPUB Creators only need to follow EPUB requirements to meet this criterion, they are still encouraged to provide additional methods to improve access beyond the minimum. Some suggestions include:

• adding at least one link to every Content Document in the spine to the table of contents, when feasible;

• adding an index to locate major topics; and

• adding additional navigation aids to the EPUB Navigation Document (e.g., lists of figures and tables).

4.2.3 ACCESS-003: Ensure the order of table of contents entries matches linear order

The table of contents provides users more than just links into the content. It is also a means to understand the structure and ordering of an EPUB Publication. Consequently, users may have difficulty locating where they are in a publication, where they want to go, and also how to return to previous locations when the order of entries in the table of contents does not match the linear reading order.

EPUB Creators should therefore ensure that the entries in the table of contents always match the linear order of the content. Specifically, the order of entries should reflect both:

• the order of EPUB Content Documents in the spine; and
• the order of each referenced section within its respective Content Document.

Only if there is a logical case for an alternative arrangement of entries should the ordering differ. Such scenarios typically only occur when the content does not have to be read linearly or when additional information is included at the end of a table of contents. For example, the table of contents for a magazine might be ordered to list all the major articles first, followed by features, etc.

When the ordering of the table of contents does not match the content, EPUB Creators should include an explanation why in the accessibility summary.

EPUB Creators should avoid including links to supplementary content at the end of the table of contents. Links to figure, tables, illustrations and similar content is better included as a separate navigation elements (either in the EPUB Navigation Document or in the spine). EPUB Creators can include links to these additional navigation lists in the table of contents.

4.3.1 SEM-001: ARIA roles and epub:type

Although the role attribute may seem similar in nature to the type attribute [EPUB-3], their target uses in EPUB Content Documents do not overlap.

The key difference between these attributes is that the role attribute bridges accessibility in content while the type attribute provides hooks to enable Reading System behaviors. Omitting roles lessens the accessibility for users of Assistive Technologies, in other words, while omitting types diminishes certain functionality in Reading Systems (e.g., pop-up footnotes or special presentations of the content).

Since each attribute offers different advantages, it is not necessary that they be used together. Due to the lack of restrictions on where EPUB Creators can use the type attribute, pairing the attributes may cause accessibility issues (e.g., putting roles on the [HTML] body element).

In particular, the use of the type attribute is not a means of satisyfing requirements for ARIA roles in WCAG.

For EPUB Creators looking to move from the type attribute to using ARIA roles, the EPUB Type to ARIA Role Authoring Guide guide details notable authoring differences between the two attributes. It also includes a mapping table of semantics in the EPUB Structural Semantics Vocabulary to equivalent ARIA roles in [DPUB-ARIA-1.0] and [WAI-ARIA-1.1].

4.3.2 SEM-002: Do not repeat semantics across chunked content

Although EPUB Publications appear as single contiguous documents to users when read, they are typically composed of many individual EPUB Content Documents. This practice keeps the amount of markup that has to be rendered small to reduce the load time in Reading Systems (i.e., to minimize the time the user has to wait for a document to appear). It is rare, at least for books, for an EPUB Publication to contain only one Content Document with all the content in it.

When content is chunked in this way, it often requires the EPUB Creator to make decisions about how best to restructure the information. A part, for example, will typically not include all the chapters that belong to it. The EPUB Creator will instead separate the part heading from each chapter, putting each into a separate document.

Although visually these restructuring decisions can be hidden from readers, they impact the functionality of Assistive Technologies. In the case of [WAI-ARIA-1.1] roles, the result is that only the subset present in the currently-loaded EPUB Content Document are exposed to users. An Assistive Technology cannot provide a list of landmarks for the whole publication, as it cannot see outside the current document.

To counteract this destructuring effect, EPUB Creators sometimes think to re-add or re-identify structures in the belief that having this information in every document will be helpful to users (e.g., adding an extra [HTML] section element around a chapter to indicate it belongs to a part, or putting the part semantic on the body tag). All this practice does, however, is add repetition that is not only disruptive when reading but can make the structure of the publication harder to follow. EPUB Creators are therefore advised not to attempt to rebuild structures in these ways.

For example, consider a book that has five parts and each part contains five chapters. Structurally, each chapter belongs to its part (i.e., is grouped with it), as in the following markup:

<section role="doc-part">
   <h1>Part 1</h1>
   
   <section role="doc-chapter">
      <h2>Chapter 1</h2>
      …
   </section>
   …
</section>

Since this would lead to a large content file, the part heading is typically split out into its own Content Document so that it will appear on its own page:

<html … >
   …
   <body role="doc-part">
      <h1>Part 1</h1>
   </body>
</html>

Each chapter is then separated into a separate Content Document:

<html … >
   …
   <body role="doc-chapter">
      <h2>Chapter 1</h2>
   </body>
</html>

It is not necessary to add a part wrapper to each chapter, as in the following example:

<html … >
   …
   <body role="doc-part">
      <section role="doc-chapter">
         <h2>Chapter 1</h2>
         …
      </section>
   </body>
</html>

Doing so introduces a new part landmark into each document, which will cause an Assistive Technology to inform the user that the landmark is available to navigate to.

4.3.3 SEM-003: Include EPUB landmarks

[WAI-ARIA-1.1] landmarks are similar in nature to EPUB landmarks [EPUB-3]: both are designed to provide users with quick access to the major structures of a document, such as chapters, glossaries and indexes. ARIA landmarks are compiled automatically by Assistive Technologies from the roles that have been applied to the markup, so EPUB Creators only need to follow the requirement to include roles for the landmarks to be made available to users.

Although automatic generation of ARIA landmarks simplifies authoring, it also means that ARIA landmarks are limited to how the EPUB Publication has been chunked up into Content Documents. An Assistive Technology can only present the landmarks available in the currently-loaded document; it cannot provide a complete picture of all the landmarks in a multi-document publication (see the previous section for more discussion about content chunking).

EPUB landmarks, on the other hand, are compiled by the EPUB Creator prior to distribution, and are not directly linked to the use of the type attribute [EPUB-3] in the content. They are designed to simplify linking to major sections of the publication in a machine-readable way, as Reading Systems do not scan the entire publication for landmarks, either. EPUB landmarks are typically not as numerous as ARIA landmarks, as Reading Systems only expose so many of these navigation aids.

Given these differences in application, however, it is important to include EPUB landmarks and not rely only on the presence of ARIA roles to facilitate navigation, and vice versa. Each aids navigation in its own way.

The EPUB specification does not require that EPUB Creators include a specific set of landmarks, but it is recommended to include a link to the start of the body matter as well as to any major reference sections (e.g., table of contents, endnotes, bibliography, glossary, index).

4.4.1 TITLES-001: Include publication and document titles

[WCAG2] Success Criterion 2.4.2 requires that each Web page include a title. EPUB has a similar requirement for EPUB Publications: publications require a [DCTERMS] title element in the Package Document metadata. The [WCAG2] requirement is not satisfied by the EPUB requirement, however.

When authoring an EPUB Publication each EPUB Content Document also requires a descriptive title that describes its content. If not provided, Assistive Technologies often will announce the name of the file to users.

If the title includes structural context (e.g., the part heading a chapter belongs to, or the name of the publication), order the title such that the most precise description of the current document comes first.

For more information about titles, see Technique H25.

4.4.2 TITLES-002: Ensure numbered headings reflect publication hierarchy

To a user, an EPUB Publication appears as a single document that they read from beginning to end, even though the content is often split across numerous EPUB Content Documents. As a result, their natural expectation is that the headings reflect their position in the overall hierarchy of the publication, despite the publication not actually being a single document (e.g., if a part heading is expressed in an [HTML] h1 element, each chapter that belongs to the part will have an h2 heading).

Technique G141: Organizing a page using headings instructs EPUB Creators on correctly using numbered headings within a document, but with EPUB Publications the numbered headings also need to remain consistent across documents. Practically, this means that each EPUB Content Document does not have to begin with an h1 heading unless the first heading is a top-level heading — the first heading needs to have a numbered heading element that reflects its actual position in the publication.

EPUB Creators also to need chunk their content so that the first heading in a document always has the highest number. For example, if a document starts with an h3 heading, there should not be an h2 heading later in the document (e.g., do not include the start of a new section with the trailing subsections of the previous). It is acceptable for there to be subsequent headings at the same level as the first (e.g., multiple subsections in one document could all have h3 headings).

4.5.1 DESC-001: Include alternative text descriptions

The first version of these techniques only required alternative text for images regardless of their complexity. This exception is no longer valid.

EPUB Creators must now ensure that their image-based content meets [WCAG2] requirements for alternative text and extended descriptions to conform with [EPUB-A11Y-11].

5.1.1 PAGE-001: Provide page break markers

Both the EPUB Structural Semantics Vocabulary [EPUB-SSV] and Digital Publishing WAI-ARIA 1.0 Module [DPUB-ARIA-1.0] include a semantic for static page breaks: pagebreak and doc-pagebreak, respectively.

It is recommended that both semantics be applied to EPUB 3 content to ensure maximum compatibility with Reading Systems and Assistive Technologies.

A title or aria-label attribute is required on the element, as it provides the value that is announced to the user. Do not include the page number as text content, as this practice forces the user to hear it announced wherever it occurs (e.g., without any context in the middle of a sentence).

EPUB 2 does not include markup to identify static page break marks in the content. Page break destinations can be included to enable hyperlinking, but the page list is the only way a user can jump to the locations.

Do not use the [HTML] a element to identify page break locations in EPUB 3 Publications. Although this element was previously defined as the anchor for a hyperlink destination, its purpose has been changed in [HTML] for use solely as a link.

5.1.2 PAGE-002: Identify pages in audio playback

Readers rarely stop reading to review each new page number, so when page numbers are read aloud in the audio playback of a publication it is not only distracting, but can be confusing, as well (e.g., the number could be read out in the middle of a sentence).

To mitigate this potential annoyance to readers, EPUB Creators need to identify page announcements in the EPUB 3 media overlays document when they are included. Identification allows a Reading System to provide a playback experience where the numbers are automatically skipped.

To identify page numbers in EPUB 3 Publications, attach an epub:type attribute with the value "pagebreak" [EPUB-SSV] to each par element [EPUB-3] that identifies a page number in the media overlay documents.

Note that as EPUB 2 does not provide text and audio synchronization, this technique does not apply.

5.1.3 PAGE-003: Provide a page list

A page list — a list of hyperlinks to the static page break locations — is the most effective way for users to find static page locations. Without a page list, the user would have to navigate each page marker in the text, provided they are available and the Reading System provides such functionality.

When a page list is included, Reading Systems can provide users direct access to the list or use it to provide automatic page jump functionality.

The EPUB Navigation Document allows the inclusion of a page-list nav [EPUB-3], while the EPUB 2 NCX file provides the same functionality through the pageList element [OPF-201].

5.1.4 PAGE-004: Identify the pagination source

Users typically want to know the source of the page break markers included in an EPUB Publication when they are derived from a static media. Considerations like which printing, by which publisher or imprint, and whether the pagination comes from the hard or soft cover edition will affect decisions about its usefulness (e.g., does it exactly match the pagination of a print book used in a classroom).

To allow users to determine the suitability of the pagination, identify the ISBN of the source work in the Package Document metadata.

EPUB 3 allows the source of pagination to be explicitly identified using the source-of property with the value "pagination" [EPUB-33].

The source-of property is particularly useful when there are multiple sources for an EPUB Publication as it disambiguates which one the pagination came from.

If an ISBN is not available, include as much information as possible about the source publication (e.g., the publisher, date, edition, and binding).

If the page break markers are unique to the EPUB Publication, do not identify a print source.