Exception Handling in Component-Based System Development

Designers of component-based software face two problems related to dealing with abnormal events: developing exception handling at the level of the integrated system and accommodating (and adjusting, if necessary) exceptions and exception handling provided by individual components. In this paper our intention is to develop an exception handling framework suitable for component-based system development by applying general exception handling mechanisms which have been proposed and successfully used in concurrent/distributed systems and in programming languages. The framework is applied in three steps. Firstly, individual components are wrapped in such a way that the wrappers perform activity related to local error detection and exception handling, and signal, if necessary, external exceptions outside the component. At the second step the execution of the overall system is structured as a set of dynamic actions in which components take parts. Such actions have important properties which facilitate exception handling: they are atomic, contain erroneous information and serve as recovery regions; also, actions can be nested so that systems can be developed recursively. The last step is designing exception handling at the action level: each action (i.e. all components participating in it) handles exceptions signalled by individual wrapped components.