function DataSet(xmldoc, tagLabel) {
 this.rootObj = xmldoc.getElementsByTagName(tagLabel); 
}

DataSet.prototype.getCount=function(){
 return this.rootObj.length;
}

DataSet.prototype.getChildsNode=function(index){
  return this.rootObj[index].childNodes;
}

DataSet.prototype.getCount=function(){
 return this.rootObj.length;
}

DataSet.prototype.getAttribute=function(index, tagName) {
 if (index >= this.count) return "index overflow";
 var node = this.rootObj[index];
 var str = node.getAttribute(tagName);
 return str;
}