Note:
When submitting data to a URL, we recommend that you specify an absolute target. Relative targets are interpreted relative to the user environment, which can vary from one user to the next at run time.
This format submits an XML data stream, which allows for the hierarchical representation of data and can be parsed by any generic XML parser. Choose this format if the server that communicates with the run-time user application program must receive an XML data steam.
See also 

To insert a submit button that sends an XML data stream