This may be a stupid question, but can someone explain the advantages of XML over HTML.
XML is a data delivery method. Like html is to php for display, so is and can be html to XML. XSLT Sheets parse XML feed data and display that to visitors using html usually. PHP apps can recieve data in xml format and work with it like you work with an array. The structure of the xml records sent is predefined usually so you know what to expect so you can work with it. Although it can be sent blind and functions to just display it all can be coded.
Pick out the keywords and run them through your favorite search engine as suggested.