An XMLRPC client is required to send commands to TerrainView™. The client is responsible for the conversion of the RPC data like procedure name and arguments into an XML description and to post the XML via HTTP to the XMLRPC server integrated in TerrainView™.
The official XMLRPC specification is rather short and definitely worthwhile reading. It can be found on http://www.xmlrpc.com/spec. Another good resource for information about XMLRPC is http://en.wikipedia.org/wiki/Xmlrpc