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• To schedule deferred processing against application state in a fault tolerant fashion. For example if you need to schedule work to be done at a later date, you can inject a message with a delay and it will be queued for deferred execution.
• If processing of a message must be done by another thread, the results of that thread's processing can be injected back into the engine with a message. 
• If you are working with a 3rd party library or other application locally that does processing that may be based on the local environment, you add the results of that processing to message and inject into it back into the engine for fault tolerant processing. In this case you might also consider using environment based replication (see below). 

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