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A Very-Quick-&-Very-Dirty Overview to File Formats and Accessibility

ASCII, HTML, and XML computer and Web formats are flexible, simple, and, most importantly, compatible with most assistive technology devices if coded with accessibility in mind.

ASCII (American Standard Code for Information Interchange) is the most common format for text files in computers and on the Internet.

HTML (Hyper Text Markup Language) is the set of codes (or markup symbols) inserted in a file that is intended for posting on a Web site. The codes tell the Web browser how to display the page's words and images to the user. HTML is not inherently accessible. Web designers can rely on either the Federal Government's Section 508 Guidelines or the World Wide Web Consortium's (W3C) Web Content Accessibility Guidelines as a reference in creating accessible HTML web pages.

XML (Extensible Markup Language) is a simple, very flexible text format used to define new markup languages that can be used to address the limitations of HTML. Based on ASCII text, XML is portable in that XML-based languages can be used across different platforms and devices. XML and HTML are similar in that both define the text size, color and position, both use defined tags (XML tags are user defined), and both define the layout of information on a page.

The accessibility benefit is that a single file in XML can be rendered differently to different users. Therefore, users with assistive technology devices such as a screen reader can have the same information presented in the most appropriate manner for their devices.

However, like HTML, web designers can design their XML-based language in such a way to render it inaccessible. Currently, the W3C has a working draft accessibility standard: XML Accessibility Guidelines.

Examples of XML-based languages used in education include DAISY (a electronic textbook format) and MathML (which can display mathematical expressions on a web page). More information about XML and its accessibility issues can be found at http://www.washington.edu/accessit/articles?26.

PDF (portable document format) is a file format developed by Adobe Systems which allows documents to be transmitted electronically with their original formatting intact.

These files can be opened in any operating system (Macintosh, Windows, Unix); however, they cannot be altered or edited. This is because the files are graphical; in effect, PDF provides exact pictures of each page of a document.

These PDF files are convenient in two respects. One, it allows the originator of the document to make sure that his or her document is read in the format designed for it (correct size typeface, layout, placement of text and tables, etc.). Two, it allows the non-originator distributor of the document to avoid the labor-intensive and error-creeping-in task of converting a document into a transmittable format which approximates the originator's version.

Since PDF files are graphics-based rather than text-based, they may have limited compatibility with software text readers. This means if a professor provides the course syllabus or assignments in a non-accessible PDF file, the students who use assistive technology would not be able to obtain either independently. Instead, they are in the position comparable to a person who uses a wheelchair to be carried up a set of stairs: they would have to rely upon other people or supports to obtain the course information, or worse, be without the information and risk failing the course. [It should be noted that Adobe is trying to address the problem through incorporating new accessibility features within its software. http://www.adobe.com/accessibility/.]