1. A method of specifying an asynchronous web service within a procedural programming environment, the method comprising: providing a source code representation of at least a portion of web service logic, the logic including at least one method declared to be a callback method; and identifying a member variable declared to implement said callback method to cause a compiler to generate a client proxy object for interacting asynchronously with the client using said callback method, and to assign the client proxy object to said member variable.