A Data Island can be used to access the XML file.
To get your XML document "inside" an HTML page, add an XML Data Island to the HTML page:
<xml src="cd_catalog.xml" id="xmldso" async="false"></xml>
With the example code above, the XML file "cd_catalog.xml" will be loaded into an "invisible" Data Island called "xmldso". The async="false" attribute is added to make sure that all the XML data is loaded before any other HTML processing takes place.