Object Transaction Service Research Articles

Unification of transactions and replication in three-tier architectures based on CORBA

In this paper, we describe a software infrastructure that unifies transactions and replication in three-tier architectures and provides data consistency and high availability for enterprise applications. The infrastructure uses transactions based on the CORBA object transaction service to protect the application data in databases on stable storage, using a roll-backward recovery strategy, and replication based on the fault tolerant CORBA standard to protect the middle-tier servers, using a roll-forward recovery strategy. The infrastructure replicates the middle-tier servers to protect the application business logic processing. In addition, it replicates the transaction coordinator, which renders the two-phase commit protocol nonblocking and, thus, avoids potentially long service disruptions caused by failure of the coordinator. The infrastructure handles the interactions between the replicated middle-tier servers and the database servers through replicated gateways that prevent duplicate requests from reaching the database servers. It implements automatic client-side failover mechanisms, which guarantee that clients know the outcome of the requests that they have made, and retries aborted transactions automatically on behalf of the clients.

Integration of CORBA and object relational databases

CORBA is widely accepted as the open international standard for modelling and building comprehensive distributed systems. In most cases, CORBA architects have adopted relational databases for storage of persistent data. Among the issues that usually face architecture designers considering how to combine CORBA and standard relational database standards are fault tolerance, performance, and the extensibility and scalability of the systems. The research team involved with this paper found that the ODMG object database concept is useful to solve the issues encountered when integrating CORBA and relational database standards. The reference architecture, which the team devises, integrates CORBA and relational databases without compromise on the necessary transactional properties. The CORBA standard object transaction service and concurrency control service are reused. The team also develop an object relational data modelling tool—Latte—that supports the overall design intention as well the development paradigms for the proposed architecture. The implementation of the system is useful to CORBA, ODMG, and relational database architects because it provides a unified modelling and programming paradigm capable of solving the problems of managing mission-critical distributed data. Thus, we present a case study of combining different international standards to build a comprehensive system.

A new architecture for integration of CORBA and OODB

Object oriented database system (OODB) supports an object oriented data model with the functionality of persistency and transaction semantics. In order to facilitate the use of OODB, the Object Database Management Group (ODMG) defined a standard for object database management systems. On the other hand, the Object Management Group (OMG) defined the Common Object Request Broker Architecture (CORBA), which is an emerging standard of distributed object technology providing the interconnection network between distributed objects. For the sake of matching these two object models, taking the advantages of merging both of them, and building a more sophisticated infrastructure, the integration of CORBA and OODB is currently an urgent and important issue in distributed object systems. Instead of using Object Database Adapter (ODA) suggested by the ODMG, we provide a novel way of reusing the Object Transaction Service (OTS) and wrapping techniques to introduce OODB into CORBA automatically. Through our design, CORBA clients or OODB object implementers do not need to learn any knowledge of each other. In addition, error recovery is also provided to guarantee the consistency of object states. The whole task for integrating CORBA and OODB is done transparently by our proposed preprocessor, which plays an important role in solving problems encountered by ORB and OODB vendors easily.

Object Management Group object transaction service based on an X/Open and International Organization for Standardization open systems interconnection transaction processing kernel

This paper addresses federation of a transactional object standard - Object Management Group (OMG) object transaction service (OTS) - with the X/Open distributed transaction processing (DTP) model and International Organization for Standardization (ISO) open systems interconnection (OSI) transaction processing (TP) communication protocol. The two-phase commit propagation rules within a distributed transaction tree are similar in the X/Open, ISO and OMG models. Building an OTS on an OSI TP protocol machine is possible because the two specifications are somewhat complementary. OTS defines a set of external interfaces without specific internal protocol machine, while OSI TP specifies an internal protocol machine without any application programming interface. Given these observations, and having already implemented an X/Open two-phase commit transaction toolkit based on an OSI TP protocol machine, we analyse the feasibility of using this implementation as a transaction service provider for OMG interfaces. Based on the favourable result of this feasibility study, we are implementing an OTS compliant system, which, by initiating the extensibility and openness strengths of OSI TP, is able to provide interoperability between X/Open DTP and OMG OTS models.

The impact of object technology on commercial transaction processing

Businesses today are searching for information solutions that enable them to compete in the global marketplace. To minimize risk, these solutions must build on existing investments, permit the best technology to be applied to the problem, and be manageable. Object technology, with its promise of improved productivity and quality in application development, delivers these characteristics but, to date, its deployment in commercial business applications has been limited. One possible reason is the absence of the transaction paradigm, widely used in commercial environments and essential for reliable business applications. For object technology to be a serious contender in the construction of these solutions requires: – technology for transactional objects. In December 1994, the Object Management Group adopted a specification for an object transaction service (OTS). The OTS specifies mechanisms for defining and manipulating transactions. Though derived from the X/Open distributed transaction processing model, OTS contains additional enhancements specifically designed for the object environment. Similar technology from Microsoft appeared at the end of 1995. – methodologies for building new business systems from existing parts. Business process re-engineering is forcing businesses to improve their operations which bring products to market. Workflow computing, when used in conjunction with “object wrappers” provides tools to both define and track execution of business processes which leverage existing applications and infrastructure. – an execution environment which satisfies the requirements of the operational needs of the business. Transaction processing (TP) monitor technology, though widely accepted for mainframe transaction processing, has yet to enjoy similar success in the client/server marketplace. Instead the database vendors, with their extensive tool suites, dominate. As object brokers mature they will require many of the functions of today's TP monitors. Marrying these two technologies can produce a robust execution environment which offers a superior alternative for building and deploying client/server applications.

Middle East Technical University Software Research and Development Center

Middle East Technical University (METU) is the leading technical university in Turkey. The Software Research and Development Center was established by the Scientific and Technical Research Council of Turkey (TUBITAK) at the Department of Computer Engineering of METU in October 1991. The aim of this center is twofold: to lead large scale software research and development projects, and to foster international cooperation. SRDC is involved in a number of research and development projects supported by the government, industrial companies and international organizations. Although SRDC projects also cover other fields of computer science, the main emphasis is on database systems. SRDC is organized around the ongoing projects and several engineers and graduate students work in these projects: M. Altinel, B. Arpinar, I. Cingil, Y. Ceken, C. Dengi, E. Gokkoca, C. Evrendilek, P. Karagoz, E. Kilic, P. Koksal, S. Mancuhan, S. Nural, F. Ozcan, G. Ozhan, V. Sadjadi, N. Tatbul. Its infrastructure includes a LAN with Sun Workstations and PCs and commercial software like Oracle7, Sybase, Informix, Adabas D, Ingres and DEC's ObjectBroker. SRDC is a beta test site for several products including SunSoft's Joe and Concerto and Orbix's Object Transaction Service. The remainder of this report describes the main projects.