%access.class; Accessibility Class Elements

Elements added to make it easier to process books and book parts in ways that are more accessible to people and devices with special needs, for example, the visually handicapped. <alt-text> is a short phrase description of an objects, <long-desc> is a more complete description of the content or intent of an object.
Declaration
<!ENTITY % access.class "alt-text | long-desc"                       >