The Standards
WCAG 2.0 Guidelines:
Guideline 1.3.1 “Info and Relationships: Information, structure, and relationships conveyed through presentation can be programmatically determined or are available in text. (Level A)” (W3C)
What do the Standards Mean?
The markup language HTML is what determines text formatting on the web. Unfortunately, html does not work for mathematical equations. For this reason, many equations on the web are simply images of text saved in formats such as JPEG, PNG, GIF, etc. Equations displayed as image files are not accessible to people who rely on screen readers because screen readers are designed to only read text formatted by markup language.
There are two primary methods to make equations on the web accessible to all users:
- Add alt text if the equations are saved as image files. The alt text should spell out the names of each of the symbols in the equation. For example, for the equation 2(4y+1) = 3y, the alt tag would state, “2 open paren 4 y plus 1 close paren equals 3 y.”
- Instead of using image files, it is recommended that you use a software or an online tool that allows you to produce equations in accessible formats using mathematical markup language (e.g MathML).
What is MathML?
MathML is a mathematical markup language. Merriam-Webster defines a markup language as, “a system (such as HTML or SGML) for marking or tagging a document that indicates its logical structure (as paragraphs) and gives instructions for its layout on the page especially for electronic transmission and display.” The markup language, MathML, is the accessible, W3C-approved way for displaying equations. Most web browsers support it either directly or with a plugin.
| MathML Code | Text Display |
|---|---|
| <math xmlns=”http://www.w3.org/1998/Math/MathML”><mn>2</mn><mo>(</mo><mn>4</mn><mi>y</mi><mo>+</mo><mn>1</mn><mo>)</mo><mo> </mo><mo>=</mo><mo> </mo><mn>3</mn><mi>y</mi></math> | 2(4y+1)=3y |
While adding descriptive alt text to equations that are displayed as images, the preferred method for making equations accessible is to use a software or a tool that will produce an equation using markup language such as MathML. If you are interested in learning about the technical aspects of MathML, review this W3C page on MathML Fundamentals.
How do you use MathML?
The easiest way to produce MathML is to use an equation tool that supports it. An example is the MathType integration for Microsoft Word. When this product is installed, the user can click a button in the toolbar in Microsoft Word to insert an accessible equation into a document.
You can review this W3C wiki for a list of MathML supported tools for more information on this topic.