Designing Accessible Web Pages

Graphs, pdf's and Charts

Graphs and charts are very often used to convey important information in a cogent and compact way. However, many times they are unusable by the learning and visually disabled. It is important therefore to provide summary information about your graph/chart either via a link to another page, or in the body of text next to your graph/chart. HTML has a LONGDESC attribute that would allow users to link to a explanatory document. This feature of HTML 4.0 is not supported by all browsers, nor is it a part of any known authoring tool. This link will take you to W3C's site and a brief introduction to LONGDESC tags, scroll down to section 2.7.3 'Long Descriptions for Images'.

Portable Document Formats or pdf's are one of the most widely used file formats for displaying information on the web. Now there are two aspects regarding the creation of pdfs for this use:

1. The original document is written in a word-processor (e.g. Microsoft Word) or some such software, and it is then converted into pdf using the features of Adobe's Acrobat software. This file is then published on the Web
2. The original document is converted into a binary file using a scanner, and then published on the Web.

If the first method of making a pdf is used, then Adobe Acrobat offers a function (a plug-in called Adobe Access) which is able to help a screen-reader read the corresponding pdf.

The problem with the second method is that the scanned file is exactly like an image. It is a collection of picture elements that the computer does not recognize, like it does text. As a result, such a document is not accessible.

So if you are converting a file to pdf, use the first method and mention on your page that that pdf file is accessible.

You can look up access.adobe.com for more information regarding this file format.

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