Flexible exception handling in the OPERA process support system

Exceptions are one of the most pervasive problems in process support systems. In installations expected to handle a large number of processes, having exceptions is bound to be a normal occurrence. Any programming tool intended for large, complex applications has to face this problem. However, current process support systems, despite their orientation towards complex, distributed, and heterogeneous applications, provide almost no support for exception handling. This paper shows how flexible mechanisms for failure handling are incorporated into the OPERA process support system using a combination of programming language concepts and transaction processing techniques. The resulting mechanisms allow the construction of fault-tolerant workflow processes in a transparent and flexible way while ensuring reusability of workflow components.