Of course, the detection of a value fault can be handled by consistency checks at any point in a system. In distributed systems, most of the facilities available to the conventional communications programmer should be visible to the applications programmer, but em only when wanted. The object model provides us with a convenient way of inheriting base methods. These can include base exceptions for handling timeouts and such events. Any operating system or application has to provide services within time constraints.
Some constraints are looser than others.
A system must provide varying degrees of reliability. Some data may not be recoverable and some sequences of events may not be repeatable. The relative costs of fixing or preventing faults are different at different stages of a system design and implementation.