What's the best and most elegant way to represent a web service interface using a UML class diagram?
Well it is just a diagram to help pass a point so whatever is clear. One option is to use stereotypes put "contract" on the interface and put "web service" on the class.
Martin Spamer
I would use a Sequence Diagram not a Class Diagram.
来源：https://stackoverflow.com/questions/12459912/how-to-draw-a-web-service-using-uml