Bookmarklets | MOVABLE TYPE According to Dave Winer, XML RPC "is a spec and a set of implementations that allow software running on disparate operating systems, running in different environments to make procedure calls over the Internet. It's remote procedure calling using HTTP as the transport and XML as the encoding. XML-RPC is designed to be as simple as possible, while allowing complex data structures to be transmitted, processed and returned."
RPC is a very simple extension to the procedure call idea, it says let's create connections between procedures that are running in different applications, or on different machines. The procedure call is remote (RPC stands for Remote Procedure Call). XML-RPC uses XML as the marshalling format. An XML-RPC message is an HTTP-POST request. The body of the request is in XML. A procedure executes on the server and the value it returns is also formatted in XML.
The thing is that it is possible to make query on google via XML-RPC : google gateway/