Now, all you need is a standard on top of that platform - and here is exactly where SOAP steps in. In all of this raving about SOAP, I should be clear that SOAP obviously does not address component technology itself. Instead, SOAP merely defines an interoperability standard between them. Simply put, SOAP consists of communication in terms of messages that are sent from client to server. So, our discussion will assume we are using SOAP over this protocol.
Servers reply with SOAP messages that contain the output values framed in a method response.
Figure 1 shows a client that is requesting prices for an old arcade game and a server that responds. SOAP messages are essentially XML documents that each contain a SOAP envelope. The envelope consists of an optional header and a required body. The header is also a means for extending the protocol, but in a decentralized manner. Figure 2 shows the specifics of the communication sketched out in Figure 1.