XPath API:
XML used to make our flash applications more dynamic.
The native XPathAPI class allows us to search the XML nodes and attributes within XML that €™s loaded in to flash.
Simple XML Structure:

Loading XML:

The basic actionscript code for loading XML in actionscript 2.0

var xml:XML = new XML();
xml.ignoreWhite = true;
xml.onLoad = function( isLoaded:Boolean )
{
  if(isLoaded)
  {
    // here this refers to the xml object. Instead of this we can also use xml there.
    trace( this );
//trace( xml );
  }else
  {
    trace("XML loading error");
  }
}
xml.load( "XML/store.xml" );

Output:
Entire xml content.

Explanation:

var xml:XML = new XML();
Declaring the xml object that holds the externally loaded XML data.
xml.ignoreWhite = true;
Ignoring the unwanted whitespaces in loaded XML.
xml.onLoad = function(){}
onLoad function triggered once the xml is loaded using xml.load method is called. onLoad function also checks whether the load is success or not.

Importing XPath API:

First step before using Xpath Api is to import the XPathAPI class. This will make us to use the methods of the XPathAPI in our code.
Import mx.xpath.XPathAPI;
Or
mx.xpath.XPathAPI.[methodName]

XPath API methods:

selectNodeList()
selectSingleNode()
XPathAPI.getEvalString()
XPathAPI.setNodeValue()

getEvalString:

A string that represents the code required to access the value specified by the path parameter from the parent node.

import mx.xpath.XPathAPI;
var xml:XML = new XML();
xml.ignoreWhite = true;
xml.onLoad = function( isLoaded:Boolean )
{
  if(isLoaded)
  {
    //trace( this );
    //  or
    //trace( xml )
    var myEvalString_str:String = XPathAPI.getEvalString(this.firstChild,"store/item/name");
    trace("getEvalString: " + myEvalString_str);
  //output
    //getEvalString: this.firstChild.childNodes.0.childNodes.0.firstChild.nodeValue
    //we can use this to locate the value, for example
    //add this.firstChild infront bcoz we give this as the first argument for getEvalString.
    //replace childNodes.0 with childNodes[0]
    trace(this.firstChild.childNodes[0].childNodes[0].firstChild.nodeValue)
  //Outputs Pencil
  }else
  {
    trace("XML loading error");
  }
}
xml.load( "XML/store.xml" );

Explanation:

Outputs:
getEvalString: this.firstChild.childNodes.0.childNodes.0.firstChild.nodeValue
this method is useful to locate the value, for example
add this.firstChild infront bcoz we give this as the first argument for getEvalString.
replace childNodes.0 with childNodes[0], this forms this.firstChild.childNodes[0].childNodes[0].firstChild.nodeValue
now trace the value and see
trace(this.firstChild.childNodes[0].childNodes[0].firstChild.nodeValue)

selectNodeList:

Method returns an array of nodes matching the given XPathAPI statement.
import mx.xpath.XPathAPI;

var xml:XML = new XML();
xml.ignoreWhite = true;
xml.onLoad = function( isLoaded:Boolean )
{
  if(isLoaded)
  {
    //trace( this );
    //  or
    //trace( xml )
    var nodeList_arr : Array = XPathAPI.selectNodeList(this.firstChild,"store/item/name");
    trace("selectNodeList: " + nodeList_arr);
    //output
    //selectNodeList: <name>Pencil</name>,<name>Eraser</name>,<name>NoteBook</name>
    //nodeList_arr contains collection of XMLNodes with nodeName as name
    //to get the values from XMLNodes use looping statements
    for(i=0;i<nodeList_arr.length;i++)trace("Value :"+nodeList_arr[i].firstChild.nodeValue);
  }else
  {
    trace("XML loading error");
  }
}
xml.load( "XML/store.xml" );

//output
//selectNodeList: <name>Pencil</name>,<name>Eraser</name>,<name>NoteBook</name>
//Value : Pencil
//Value : Eraser
//Value : NoteBook

Explanation:

store/item/name defines the path of node name (name)
we cal also use
*/*/name
This retrives the XMLNodes with nodeName €“name, selectNodeList returns array.
To get the nodeValues we need to use looping statements to loop through the array.

SelectSingleNode:

This XPathAPI method retives the XMLNode which matches the query we can also use AND, OR statements while using the query.

import mx.xpath.XPathAPI;
var xml:XML = new XML();
xml.ignoreWhite = true;
xml.onLoad = function( isLoaded:Boolean )
{
  if(isLoaded)
  {
    //trace( this );
    //  or
    //trace( xml )
    var xmlNode:Array = XPathAPI.selectNodeList(this.firstChild,"store/item[@id='1']");
    trace("selectSingleNode: " + xmlNode);
    //output
    //selectSingleNode: <item id="1"><name>Pencil</name><price>10</price><code>1120</code></item>
    //Here the query retives the node which has the attribute id ='1'
  }else
  {
    trace("XML loading error");
  }
}
xml.load( "XML/store.xml" );

Download Macromedia XPathAPI documentation

Download source files