XML Document Configuration Management (XDM)/XML Configuration Access Protocol (XCAP):
Because of the gaining prominence by XML now it is also going to use in telecommunications. It is used to storing various configurations in mobile devices and exchanging short information like supplementary services.
XDM and XCAP is designed to provide standard way of managing and exchanging information in the form of XML See the Specs 3GPP 24.623. XCAP protocol allows a client to read, write, and modify application configuration data stored in XML format on a server and allows clients to read, write as well as modify the same configuration file. XCAP maps XML document sub-trees and element attributes to HTTP URIs, so that these components can be directly accessed by HTTP. An XCAP server is used by the XCAP clients to store data like Presence policy in combination with a SIP server that supports PUBLISH /SUBSCRIBE /NOTIFY methods to provide a complete SIP SIMPLE server solution.
For more details see here.