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Web Services
Creating ABL Clients to Consume OpenEdge SOAP Web Services : Connecting to OpenEdge SOAP Web Services from ABL : What is a Web service connection?

What is a Web service connection?

Precisely speaking, there is no such thing as a Web service connection. All communication between a Web service client and the Web service is, from a network point of view, connectionless. That is, neither the client host nor the Web service host maintains any knowledge about each other except the other's location, and then only when exchanging messages. Any context or state must be managed explicitly by the application.
However, from the client application point of view, there is definitely a defined relationship between itself and the Web service it is communicating with, and this relationship is more properly defined as a binding. A binding retains a logical connection between the client application and the Web service by maintaining a continuous association between specified client resources and specified Web service resources. This is the same type of "connection" that an ABL client application maintains between itself and a session-free AppServer with which it is communicating (see OpenEdge Application Server: Developing AppServer Applications).
This binding relationship makes it easier for the client to send requests to the Web service and to manage those requests within its own environment until such time as it has no more need for the bound Web service and its resources. At such a time, the client application can logically disconnect (unbind) the Web service from its environment in order to free up resources for other tasks.
While the Web service is bound, the process of invoking a Web service request includes telling the client host where to send the application message on the Internet so the Web service can receive and respond to it. This happens every time that the client invokes a Web service request because, as noted previously, the client host maintains no knowledge of the Web service host and its relationship to the client application. This lack of a physical connection provides performance benefits. Given sufficient AppServer resources, a client never needs to wait for an AppServer to service its Web service request, and whenever an AppServer completes a request, it is free to service a request from any other client. This arrangement offers maximum scalability for a given set of AppServer resources over an increasing client load.
To take further advantage of Web service availability on the network, OpenEdge allows the ABL client to make both synchronous and asynchronous requests to a Web service, providing greater flexibility in its own request management. For more information on asynchronous Web service requests, see Managing asynchronous requests.