Requirements for accessible documents

For long time, PDF, HTML and Doc were the most used documents types not only for blind and visually impaired persons. Since a few years, new document types are arising like epub or other XML-based doc types like DocBook or DAISY.

The requirements for well established doc types are widely known. But the arising of new document types makes it necessary to reformulate the requirements independently from a special doc type.

The following requirements can be applied to all possible document types:

  • Separation of structure and design
  • Usage of semantic elements and Meta information
  • Multi sensory rule
  • Help for navigation and determine position
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Linearization and reading order

Linearization means, that texts and other doc elements have to be in the right order, if they were shown in one column. The reader must see alsoh, which element belongs to which other element. For example, a picture must be connected to the right part of the text.

The logical reading order describes, that all important elements are included in the reading stream. Not necessary elements like page numbers or headers and footers have to be excluded of the reading stream. This information’s are quite important and should be reachable for the reader, but they should not be in the reading stream, because they disturb the reader.

Separation of structure and design

The separation of structure and design allows the reader to adjust the document to his or her needs. Visually impaired can show all content in one column, persons with reading disabilities can change the font or other factors and so on.

In the future it will not be important, that a document looks the same on all platforms. Instead it will be important that documents are adaptable to the different platforms like smartphones, Tablets or beamers.

The requirements of the different groups like visually impairness, autism or reading difficulties are too difficult to fulfil and inconsistent. Most of the work will be done by their reading client and the client works better when the document is adjustable to his needs.

Structure and semantics

With the new elements of HTML5 or ePub 3 it is easier to structure documents semantically. Semantics in graphical user interfaces is for blind what is the visual design for seeing persons. Semantics allows the blind reader to understand the role of an element.

Semantic elements also allows adapting the document on different reading clients. It belongs to the already mentioned topic structure.

The multi sensory rule

The multi sensory rule means, that information must be perceivable over more than one sense. For example, a video should have captions for deaf persons or an image should have an alternative description for blind readers.

Navigation mechanisms and position determination

Navigation mechanisms make it easier to navigate through documents. -First of all there is the table of contents. For longer documents, an index or a sitemap can be useful. It is clear, that in a digital document these mechanisms have to be interactive, if you click on an element, the reading client jumps to the linked element in the text.

Beside these navigation mechanisms the reader always needs the information, where in the document he actually is. This can be difficult for blind or visually impaired persons, which cannot see the scroll bar. But this seems to be more an task for the reading client.

New requirements in digital documents

New documents like ePubs seem to define new requirements. For example, in ePub 3 you can integrate a multimedia player or forms. Of cause, they have to be accessible to.

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