--- /dev/null
+.. This work is licensed under a Creative Commons Attribution 4.0 International License.\r
+.. http://creativecommons.org/licenses/by/4.0\r
+.. Copyright 2017 Huawei Technologies Co., Ltd.\r
+\r
+BPMN Main Process Flows\r
+========================\r
+\r
+Characteristics\r
+----------------\r
+\r
+**Invoked by an API Handler**\r
+\r
+ The BPMN application (war) exposes a REST endpoint to which the API Handler(s) send requests for flow execution. The message sent by the API Handler to this endpoint is a JSON wrapper containing:\r
+ \r
+ * The original request received by the API handler from the portal or other client.\r
+ * Metadata such as the request-id generated by the API Handler for the request.\r
+ * The name of the BPMN process to execute (obtained by the API Handler from the mso_catalog.service_recipe table.\r
+ \r
+**Asynchronous Service Model**\r
+ \r
+ All main process flows implement an asynchronous service model. The connection to the API Handler is kept open until the main process flow sends back a response. In the flow shown below, this is done by the "Send Sync Ack Response" script task. A flow is expected to send a response after validating the request, but before performing any long running tasks or tasks that could cause the process to be suspended.\r
+ \r
+ After the synchronous response is sent, the flow continues to execute. When the flow ends, it may optionally send an asynchronous notification to a callback URL provided in the original request (behavior depends on the API agreement)\r
+ \r
+**Typically calls one or more subprocess flows**\r
+\r
+ Main process flows usually implement the high-level service logic, delegating the "real" work to reusable subflows (Building Blocks) or custom subflows\r
+ \r
+**Handles "Completion" and "Fallout" tasks**\r
+\r
+ "Completion" tasks are those that occur when the process ends successfully, and "Fallout" tasks are those that occur when the process fails. Activities include:\r
+ \r
+ * Updating the mso_requests database.\r
+ * Rolling back uncompleted work.\r
+ * Sending an asynchronous callback notification.\r
+\r
+Example: CreateVfModuleVolumeInfraV1.bpmn\r
+------------------------------------------\r
+\r
+.. image:: images/BPMN_Main_Process_Flows_1.png
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