What is Fault, Error, Detector, Failure, Exception

Fault – A fault is the origin of any misbehavior. It is the adjudged or hypothesized cause of an error.

Error – This is the part of a system state that is liable to lead to a failure. With respect to a fault it is a manifestation of a fault in a system. User errors are not part of the above error-definition. A user error is a mistake made by a user when operating a software system. The system is able to react to these mistakes, because it is designed to expect such situations and it is a part of the required functionality. The handling of those situations, which of course can be abnormal, should be treated in the user interface component of the system. In contrast to an error, a user error cannot result in a system crash, but like a system error, a user error normally can result in an exception raised by a system component.

Failure – A failure is a deviation of the delivered service from compliance with the specification. Whereas an error characterizes a particular state of a system, a failure is a particular event namely the transition from correct service delivery to incorrect service.

Detector – Before software can react to any error, it has to detect one first. If we look at the error handling as a separate software system, errors and failures of an application are the phenomena the error handling system observes. Thus a detector is the interface between the error and failures happening outside and their internal handling. The number, place and kind of detectors have great impact on the quality of an error handling system.

Exception – Generally, any occurrence of an abnormal condition that causes an interruption in normal control flow is called an exception. It is said that an exception is raised (thrown) when such a condition is signaled by a software unit. In response to an exception, the control is immediately given to a designated handler for the exception, which reacts to that situation (exception handler). The handler can try to recover from that exception in order to continue at a predefined location or it cleans up the environment and further escalates the exception. To raise an exception, a program first has to detect an error or failure