Scopes

Every time a workflow is run, a session is started. That session is contained within some scope. Each scope has a start operation (green play symbol) and a terminate operation (golden star).

Start

The start operation has one simple purpose: deliver the user’s request message into this session. Each time a new session starts, exactly one message will be produced by the start operation, and it will be whatever request message started this run of the workflow. The start operation will never output a second message for the same session.

Terminate

Naturally the terminate operation serves the opposite purpose of the start operation. The terminate operation has an input slot and no output slots, so it will never output a message within its own scope. Instead it takes the first message that gets passed to it for each session and then sets that as the final response of that workflow session. Any additional messages passed to it for the same session will simply be discarded.

Immediately after the terminate operation is activated, it will trigger the scope cleanup to begin. This ensures that all activity happening inside the workflow is brought to a clean and complete finish before the outside world is told that the workflow is done.

As soon as the cleanup process is finished, the first output that was passed to the terminate operation will be sent out as the final output of the workflow session.