The Exception Handler element defines the group of operations to carry out when an exception occurs. In an Activity diagram, the protected element can contain a set of operations and is connected to the exception handler via an Interrupt Flow connector. Any defined error contained within an element's parts can trigger the flow to move to an exception.
OMG UML Specification:
The OMG Unified Modeling Language specification, (v2.5.1, p.404) states:
An exception is a value used to identify a non-normal completion mode of an execution. If an exception is raised (e.g., using a RaiseExceptionAction; ...) within the execution of an ExecutableNode and not handled within that execution, then the execution is terminated and the exception is propagated out of the ExecutableNode.
An ExecutableNode may have one or more ExceptionHandlers that are used to deal with exceptions that may be propagated out of the ExecutableNode, which is the protectedNode of those handlers. If an exception is propagated out of the protectedNode, then the set of handlers is examined for a handler that matches the exception. A handler matches if the type of the exception is the same as, or a (direct or indirect) subtype of, one of the exceptionTypes of the handler. If there is a match, the handler catches