EPUB 3 Accessibility Guidelines

In order to facilitate the navigation of lists, Media Overlay documents must be marked up so that lists are discoverable — and consequently escapable and skippable — by the reader without having to drop out of playback mode.

Although the basic markup for lists in overlays is the same regardless of list type, HTML5 includes two different types of lists that need to be accommodated.

Ordered and Unordered Lists

The HTML ol and ul list elements each represent sets of items, and are marked up similarly as follows:

• A single seq element encloses all the items in the list. This seq must have an epub:type attribute specifying the property list.
• Complex list item (those that contain two or more synchronization points) must also be identified using seq elements. These seq elements must have an epub:type attribute specifying the property list-item. If the list item contains complex structures like sublists or tables, those structures must be marked up as appropriate to ensure escapability and skippability.
• Simple list items — containing only a single synchronization point — can be represented using par elements with an epub:type attribute specifying the property list item.

Definition Lists

HTML definition lists (the dl element) associate one or more names (dt elements) with one or more values (dd elements). When constructing these lists in an overlay document, the following markup rules should be followed:

• A single seq element should enclose all the terms and definitions in the list. This seq must have an epub:type attribute specifying the property list, idnetical to ordered and unordered lists.
• A seq elements should enclose all the related dt and dd pairings, and include an epub:type attribute specifying the property list-item.