XML Remote Procedure Calls (XMLRPC) is a W3C Standard Protocol for integrating dissimilar application interfaces. This interface is one of the original interfaces for conducting XML-Messaging between applications, and is the foundation for other protocols such as Simple Object Access Protocol (SOAP).
As of the release of the NitroMation-API, XMLRPC is becoming a commonly available interface for integrating applications, but SOAP is admittedly more popular. NitroMation will support SOAP in a near version release of the API.
Whether you are working with a language like Visual Basic, C/C++, Java, Adobe Flash or even scripting languages like php, python, tcl and the like, XMLRPC is available for just about everything. If it is not available by default, there is a library either from the code manufacturer (e.g. Microsoft, ActiveState, etc.) or someone had written a library to perform the necessary functions and procedure calls. It is not hard to find if you do not have it, a quick search of the web can easily point you in the right direction for your language of choice.
More current versions of development languages (e.g. Visual Basic.NET and similar) have XMLRPC as a standard library.