Broader goal

Have custom markup embedded in an XHTML page transformed into a language the browser (or user) understands

For example:

Embedding ChemML into XHTML and transform to SVG
Custom notation for algebra => MathML

<html>
<head><title>My Chemistry Course</title></head>
<body>
  <h1>Chemistry</h1>
  <p>This is a molecule of some amphetamine</p>
  <cml:molecule>
  <cml:atomArray>
    <cml:atom>...</cml:atom>
  </cml:atomArray>
  </cml:molecule>
 ...
</html>