DPF: example
<html>
<head>
<title>GPS location example</title>
<script type="text/javascript">
<![CDATA[
SystemEnvironment.location.format="zip code";
SystemEnvironment.location.updateFrequency="20s";
]]>
</script>
<script defer="defer" type="text/javascript"
ev:event="se:locationUpdate">
<![CDATA[
var field = document.getElementById("location");
var zipcode = SystemEnvironment.location;
field.childNodes[0].nodeValue = zipcode;
]]>
</script>
</head>
<body>
<h2>Track your location as you walk</h2>
<p>Your current zip code is: <span id="location">(please
wait)</span></p>
</body>
</html>