// extend GMarker(point, icon)
function UserMarker(point, xmlData, icon) {
  // store the marker data
  this.mrkData = xmlData;
  // marked by mark & sweep?
  this.marked = true;
  // super()
  PdMarker.apply(this, [ point, icon ]);
}
UserMarker.prototype = new PdMarker(new GLatLng(0, 0));
UserMarker.prototype.setData = function(xmlData) {
  this.mrkData = xmlData;
  this.marked = true;
}