Compensation Handler 

Used when something in a Business Process fails and requires a rollback or upstream activities (like money has to be returned to the customer). On an automatic basis in the Business Process , upstream steps in the Business Process are notified that the failure has occurred and certain transactions need to be reversed, sometimes in a sequential order. The compensation handler allows you to design the process and circumstances in which the compensation takes place. 

Catch Named Exception 

Each automated system (back-end system) or web service operation can publish their possible error codes (for instance, fault 15 is “bad data”). Those codes can be mapped to exception handlers. Each exception handler is connected to the scope that surrounds one or more steps in a Business Process . The components within that scope throws the exceptions when things go wrong and the exception handler automatically initiates the appropriate process to handle the problem. 

Catch All Exceptions 

This exception handler is configured to handle all exceptions that occur in a scope. 

Message Event 

This is similar to a Receive Activity, but it occurs only in the middle of a Business Process . Each of these elements can be a different message. 

Timer Event 

A timeout condition is set upon Activities, sets of Activities, or a Business Process as a whole, to ensure that processes complete within given amount of time. Timeout conditions also allow you to design the Business Process branch to take after a timeout condition takes place.