Indicate that an unprefixed element and all its unprefixed descendant
elements belong to a particular namespace by attaching an xmlns
attribute with no prefix:
<html xmlns="http://www.w3.org/1999/xhtml"
xmlns:xlink="http://www.w3.org/1999/xlink">
<head><title>Three Namespaces</title></head>
<body>
<h1 align="center">An Ellipse and a Rectangle</h1>
<svg:svg xmlns:svg="http://www.w3.org/2000/svg"
width="12cm" height="10cm">
<svg:ellipse rx="110" ry="130" />
<svg:rect x="4cm" y="1cm" width="3cm" height="6cm" />
</svg:svg>
<p xlink:type="simple"
xlink:href="ellipses.html">
More about ellipses
</p>
<p xlink:type="simple" xlink:href="rectangles.html">
More about rectangles
</p>
<hr/>
<p>Last Modified February 13, 2000</p>
</body>
</html>Both the html and head elements are in the
http://www.w3.org/1999/xhtml namespace.
Default namespaces apply only to elements, not to attributes.
Thus in the above example the align, rx, ry, x, and y attributes are not in any namespace.