Suppose that you'd like to provide a service to the public or to some business partners: They can send you two strings and you will concatenate them and return the string. Of course, in the real world you provide a more useful service. There are several major requirements: First, the users may be using different languages (Java, C# and etc.) and using different platforms (Windows, Linux and etc.). Your service must be accessible by different languages and platforms. Second, they will call your service across the Internet and there may be firewalls in between. Your service must be able to go through firewalls
