Use the documentation for the Mathematical Markup Language (MathML) Tag Set. (http://www.w3.org/TR/MathML3/).
The @alttext attribute is used only within the mathematical expressions of MathML. The equivalent function, providing words that can be display “behind” a graphic or be pronounced over a graphic, is performed by the <alt-text> element for graphics (and other elements) within this Tag Set.
| Value | Meaning |
|---|---|
| Text, numbers, or special characters | Use MathML documentation. |
| Restriction: | |