There are many web service providers that require nothing more than URL parameter passing to request a service. These service providers take HTTP/HTTPS request parameters as appended to a prospective consumer's URL, and process requests according to the passed parameter values. Services are delivered back to the requestor through the client's HTTP/HTTPS response message or as a separate HTTP/HTTPS request message exchange.
An example of such a real world web service is the PayPal Payments Standard payment processing service. This web service expects requests to come in on an advertised URL with request particulars appended to the URL as request parameters. Prospective consuming systems send HTTP/HTTPS request messages to the PayPal URL asking for service. Once a request for service has been accepted by PayPal, the Payments Standard web service responds and delivers service using the HTTP/HTTPS response message.
A separate web service, also involving...