An XML data island is XML data embedded into an HTML page.
Here is how it works; assume we have the following XML document ("note.xml"):
<xml id="note"><note> <to>Tove</to> <from>Jani</from> <heading>Reminder</heading> <body>Don't forget me this weekend!</body></note></xml>
Then, in an HTML document, you can embed the XML file above with the <xml> tag. The id attribute of the <xml> tag defines an ID for the data island, and the src attribute points to the XML file to embed:
<html><body><xml id="note" src="note.xml"></xml></body></html>
However, the embedded XML data is, up to this point, not visible for the user.
The next step is to format and display the data in the data island by binding it to HTML elements.