WCAG 1.0 Double A Checkpoint 3.1

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“When an appropriate markup language exists, use markup rather than images to convey information. ”

Using markup (and style sheets) where possible rather than images (e.g., a mathematical equation) promotes accessibility for the following reasons:

  • Text may be magnified or interpreted as speech or Braille.
  • Search engines can use text information.

There are many markup languages in widespread use today. The most obvious ones are HTML, XHTML, and CSS. See the list at the bottom of this page for some of the more popular markup languages.

MathML Example

MathML (Mathematical Markup Language) is a popular markup language used to describe complex mathematical equations.

Before

We would have to use an image to display a simple mathematical equation like this:

Depiction of a mathematical equation.

After

Now we can use the standard markup language MathML to create this equation as text. This makes your pages lighter and more accessible to assistive technologies and search engines.

<mrow>
  <mi>x</mi>
  <mo>=</mo>
  <mfrac>
    <mrow>
      <mrow>
        <mo>-</mo>
        <mi>b</mi>
      </mrow>
      <mo>±</mo>
      <msqrt>
        <mrow>
          <msup>
            <mi>b</mi>
            <mn>2</mn>
          </msup>
          <mo>-</mo>
          <mrow>
            <mn>4</mn>
            <mo>⁢</mo>
            <mi>a</mi>
            <mo>⁢</mo>
            <mi>c</mi>
          </mrow>
        </mrow>
      </msqrt>
    </mrow>
    <mrow>
      <mn>2</mn>
      <mo>⁢</mo>
      <mi>a</mi>
    </mrow>
  </mfrac>
</mrow>
		

List of Markup Languages

There are many markup languages. The following is not intended to be a comprehensive list.

  • DocBook: A markup language for technical documentation. It was originally intended for authoring technical documents related to computer hardware and software but it can be used for any other sort of documentation.
  • MathML: Mathematical Markup Language (MathML) is an application of XML for representing mathematical symbols and formulae, aimed at integrating them into World Wide Web documents.
  • SVG: Scalable Vector Graphics (SVG) is an XML markup language for describing two-dimensional vector graphics, both static and animated, and either declarative or scripted.
  • Open eBook: Open eBook (or OeB) is the e-book format based on XML format and defined by Open eBook Publication Structure Specification (OeBPS).
  • TEI: The Text Encoding Initiative publishes a set of Guidelines which specify encoding methods for machine-readable texts, chiefly in the humanities, social sciences, and linguistics.
  • XBRL: XBRL (eXtensible Business Reporting Language) is an emerging XML-based standard to define and exchange business and financial performance information.

Reference

WCAG: Markup Instead of Text