Web Services Interactions

Web services are designed to connect a client application to a service application across the Internet. While simple in concept, many layers of interactions must occur for this connection to work. Here is how a typical interaction works between a COM-based Web service (left) and a COM-based client application (right):

1. The creator of the Web service publishes the location of the service in the UDDI registry (either automatically or manually with SOAP messages).

2. The client recovers the Web service location from the UDDI registry (again, either automatically or manually with SOAP messages).

3. The client uses the DISCO protocol to pull the WSDL service contract (which describes the Web service in technical detail) as an XML document from the Web service location.

4. The WSDL service contract for the Web service is registered and stored in the client, making the Web service visible to COM applications on the client.

5. A Windows-based COM application makes a COM call to the Web service. The ROPE COM service intercepts the call, uses the local WSDL contract to convert the request into XML, and starts a SOAP proxy for the service. The SOAP proxy will represent the Web service on the client machine.