Request and Response Patterns
-----------------------------

The request and response patterns between service requester and |VOSS Automate| is 
summarized below. For details, refer to the topics in the chapter called 
*Anatomy of an API Response*.


For synchronous operations:


1. Service Requestor sends a accessor (e.g. Get, List) request with request parameters to |VOSS Automate|.
#. Either:
   
   a. |VOSS Automate| responds synchronously with a Get/List response.
   b. |VOSS Automate| responds synchronously with a fault response.


For asynchronous operations:


1. Service Requestor sends a mutator (e.g. Add, Modify, Delete) request with parameters.
#. The Add/Update/Delete transaction is scheduled on the |VOSS Automate| transaction queue with a transactionID.
#. |VOSS Automate| responds synchronously with either:
  
   a. An Add/Update/Delete response and a transactionID. 
   #. A fault response.

#. The external system either: 
   
   a. Polls the system to retrieve the status of the transaction as needed, or
   #. Specifies a callback URL (with an optional username and password if the interface is secured (recommended)) and 
      waits for a asynchronous transaction status callback (recommended). 

      When the transaction completes, |VOSS Automate| sends an async transaction status callback message to the callback URL 
      specified in the request.

.. |VOSS Automate| replace:: VOSS Automate
.. |Unified CM| replace:: Unified CM