<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <metadata>
    <link xmlns="http://www.w3.org/1999/xhtml" rel="help" href="https://www.w3.org/TR/SVG2/shapes.html#EllipseElement"/>
    <link xmlns="http://www.w3.org/1999/xhtml" rel="match" href="ellipse-03-ref.svg"/>
    <meta xmlns="http://www.w3.org/1999/xhtml" name="assert" content="rx defaults to auto."/>
  </metadata>
  <style>
    ellipse {
      ry: 30px;
    }
  </style>
  <ellipse cx="50" cy="50" fill="none" stroke="blue" stroke-width="5"/>
</svg>

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" width="100" height="100">
  <ellipse cx="50" cy="50" rx="30" ry="30" fill="none" stroke="blue" stroke-width="5"/>
</svg>