SharePoint does not have a built in method for extracting or reading data in an XML format. However there are methods to do this. There are three ways that you can access SharePoint List Data, but it depends on where the program needs to be run.
If it (the program) is required to run client side then you can use either WebServices or the URL protocol. The web services way is the most well known and easiest to use if you’re using .NET.
The URL protocol is less well known, but still very useful from say scripting or VBA environments.
If the program is required to run at the server side then you can use the object model and the SharePoint Query Object.
For more details on these methods, please refer to the following forum: http://suguk.org/forums/thread/485.aspx