To invoke a service that is provided by others or to provide a service that others
invoke, use the Web Services system functions: Invoke, Receive, and Reply.
Invoke system function: Web Services-ReliableMessaging
You can use WS-ReliableMessaging technology to provide assurance that an Invoke message
is received by the target Web Service. To achieve the reliability, a standardized series of
messages is exchanged between the sender and the receiver. In addition, each message is sent
repeatedly until the expected acknowledgement message is received.
Receive system function
Use the Receive system function to provide
a Web Service that can be invoked. The Receive step can be at any
location in the workflow.
Reply system function
Use the Reply system function to send a response to a request that
was previously accepted through a Receive system function. The reply message is
sent to the Invoke step.
Correlating web conversations
A correlation set provides an identifier between two Web Services so that one can
identify an appropriate message from another. For example, with purchase orders, there might be
several exchanges of messages between the buyer and the seller. You need to ensure that each
message stays with the appropriate conversation.
About Web Services-ReliableMessaging
While most uses of web services find the standard messaging mode adequate for their
purposes, some applications require a mechanism to ensure that a request for a web service reached
its intended target, or that a response from a web service reached the original requesting
application.