|
Vol: 47(61) No: 1 / March 2002 Dealing with Long-Lived and Complex Transactions: the ComET Model and Development System Robert Dollinger Department of Computer Science, Technical University of Cluj_Napoca, Faculty of Automation and Computers, Baritiu 26, 3400 Cluj-Napoca, Romania, phone: (40) 64-194491, e-mail: robert.dollinger@cs.utcluj.ro Aurelian Hale Department of Computer Science, Technical University of Cluj_Napoca, Faculty of Automation and Computers, Baritiu 26, 3400 Cluj-Napoca, Romania Cristian Madularu Department of Computer Science, Technical University of Cluj_Napoca, Faculty of Automation and Computers, Baritiu 26, 3400 Cluj-Napoca, Romania Keywords: extended transactions, compensating transactions, invariants, forward recovery, development system. Abstract The management of tasks involving long-lived and complex transactional computations requires a serious reconsideration of the classical transaction concept replacing it with a more systematic approach, based on a broader perspective of the entire programming model. This paper presents the ComET (Compensation based Extended Transaction) model and its implementation ComET-DS (ComET Development System). The approach is based on a few basic principles: (1) division of large computations into steps, which are transactional processing units executed in a controlled and coordinated way, (2) possibility to compensate the effect of any step at any moment before the termination of the computation, (3) coordination and execution control of steps at the semantic level by using invariants, (4) use of script language code to capture the higher level logic of the application. The ComET-DS implements a set of high level coherent control mechanisms that are able to coordinate the execution of several simple transactions and provides basic application development instruments, like the graphical script editor and reverse engineering tool, the runtime script debugger and tracer, all of which are specialized for this programming model. References [1] Anwar,E., Chakravarthy,S., Viveros,M. – An Extensible Approach To Realizing Advanced Transaction Models”, in: “Advanced Transaction Models and Architectures”, Kluwer Academic Publishers, 1997, pp.259-276. [2] Birilis,A., Dar,S., Gehani,N., Jagadish,H.V., Ramamritham,K. – “ASSET: A System for Supporting Extended Transactions, in: Proc. of the ACM SIGMOD Int’l Conf. on Management of Data, Minneapolis, USA, Minn. June 1994. [3] Elmagarmid,A.K. – Database Transaction Models for Advanced Applications, Morgan Kaufman Publishers, Inc., 1992. [4] Jajodia,S., Kerschberg, L. – Advanced Transaction Models and Architectures, Kluwer Academic Publishers, 1997. [5] Reuter,A., Schneider,K., Schwenkreis,F. – “ConTracts Revisited”, in: “Advanced Transaction Models and Architectures”, Jajodia,S. and Kerschberg, L., eds., Kluwer Academic Publishers, USA, 1997, pp.127-151. [6] Reuter,A., Schwenkreis,F. – “ConTracts – A Low-Level Mechanism for Building General-Purpose Workflow Management-Systems”, in: Bulletin of the Technical Commmittee on Data Engineering, Vol.18, No.1, IEEE Computer Society. [7] Reuter,A.,Wachter,H. – “The ConTract Model”, in: ”Database Transaction Models for Advanced Applications”, Elmargamid,A.K. ed., Morgan Kaufman Publishers, Inc., USA, 1992, pp.229-263. [8] Schwenkreis,F. – “APRICOTS – A Prototype Implementation of a ConTract System – Management of the Control Flow and the Communication System”, in: Proc. Of the 12th Symposium on Reliable Distributed Systems, Princeton (NJ), 1993. [9] Schwenkreis,F., Reuter,A. – “The Impact of Concurrency Control on the Programming Model of ConTracts”, available from: http://www.informatik.uni-stuttgart.de/ipvr/as/personen/reuter.html |