Appendix { the Workkow Program 5 Conclusions and Future Work 4.1 Data Structures

//Suppose that the following functions have been defined that make (or cancel) the appropriate // reservations. The last two functions respectively compensate for the first two functions. if (wait(self())) abort(t);g int X_conference() f tid t1, t2, t3, t4, t5, t6; Airline* air; t1 = initiate(flight_reservation, "Delta", "6/11/1994", "6/14/94"); begin (t1); if (!commit(t1)) f t2 = initiate(flight_reservation, "United", "6/11/1994", "6/14/94"); begin (t2); if (!commit(t2)) f t3 = initiate(flight_reservation, "American", "6/11/1994", "6/14/94"); begin (t3); if (!commit(t3)) return 0; // Activity Failed else air = "American";g else air = "United";g else air = "Delta"; // Flight reservation has been made at this point t4 = initiate(hotel_reservation, "Equator", "6/11/1994", "6/14/94"); begin(t4); if (!commit(t4)) f do ft5 = initiate(cancel_flight_reservation, air, "6/11/1994", "6/14/94"); begin(t5);g while (!commit(t5)); // Compensate for the flight reservation already made return 0;g // At this point, hotel and flight reservations have both been made t5 = initiate(car_reservation, "National", "6/11/1994", "6/14/94"); begin(t5); t6 = initiate(exclusive_car_reservation, "Avis", "6/11/1994", "6/14/94", t5); begin(t6); if (wait(t5)) f // Whichever of t5, t6 completes first wins abort(t6); commit(t5);g else commit(t6); return 1; // Activity has completed successfully g execution of these transactions. Even though the functions associated with transactions in our work may appear to be similar in concept to steps, transaction management primitives can be invoked from within our functions. Contract scripts introduce their own control ow syntax, while our approach uses the control ow syntax of the host language (e.g., O++) and only introduces a small set of transaction management primitives. As with contracts, ASSET allows explicit dependencies between transactions to be expressed using the form dependency primitive. One of our future goals is to develop further the underlying transaction management system of ASSET to exploit the concurrency semantics inherent in objects 10]. This will take advantage of the semantics of objects in an object-oriented database, by considering the compatibility of class speciic operations (methods). We believe that many operations in an object-oriented database may commute. For example, operations to increase an existing employee's salary and to add a new employee to a department commute. Also, operations on an object commute provided they operate on diierent parts of the object. For example, operations that update an employee's salary and change the employee's department commute. Hence, we would like to capitalize on the semantics of objects in an object-oriented database, by taking into account the compatibility of class speciic operations (methods). Concepts and mechanisms from Multi-level transactions …