Kai-Chih Liang

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.

Prototyping an integrated information gathering system on CORBA

The sheer volume of information and variety of sources from which it may be retrieved on the Web make searching the sources a difficult task. Usually, meta-search engines can be used only to search Web pages or documents; other major sources such as data bases, library corpuses and the so-called Web data bases are not involved. Faced with these restrictions, an effective retrieval technology for a much wider range of sources becomes increasingly important. In our previous work, we proposed an Integrated Retrieval (IIR), which is based on Common Object Request Broker Architecture, to spare clients the trouble of complicated semantics when federating multiple sources. In this paper, we present an IIR-based prototype for integrated information gathering system. It offers a unified interface for querying heterogeneous interfaces or protocols of sources and uses SQL compatible query language for heterogeneous backend targets. We use it to link two general search engines (Yahoo and AltaVista), a science paper explorer (IEEE), and two library corpus explorers. We also perform preliminary measurements to assess the potential of the system. The results shown that the overhead spent on each source as the system queries them is within reason, that is, that using IIR to construct an integrated gathering system incurs low overhead.

CODEX: content-oriented data EXchange model on CORBA

Asynchronous Data Exchange (ADE) is useful in Electronic Data Interchange (EDI). It needs a well-defined mechanism to support data buffing, dispatching, and filtering. ADE is more flexible, extensible and scalable than the synchronous one. CORBA Event Service, announced by OMG, offers an easy-to-use, abstract and generic communication mechanism, while providing message delivering, dispatching and buffering by way of introducing the concept of event channels. However, it lacks some practical data exchange functions.This paper proposes the design and implementation of a system named CODEX (stand for Content-Oriented Data EXchange system), which combines the XML features and the functionality of CORBA (which stands for Common Object Request Broker Architecture) Event Service. The CODEX system equips functions of primitive data type checking, message classification, content filtering and source/destination screening. Application developers can focus more on business functions, instead of earing about the detail of data exchange. The concept and architecture of the content-oriented data exchange, provided by CODEX, can be applied to other practical computing fields in the large-scale, loosely coupled distributed computing environments.

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.

Nested Transaction and ConcurrencyControl Services on CORBA

This paper presents the exploration and integration of the object transaction service and concurrency control service based on CORBA. We provide not only the flat transaction model but also the nested transaction model. Nested transaction provides isolation of failures and enhances concurrency of long-lived transaction. Issues on supporting nested transactions in both the object transaction service and the concurrency control service are discussed. We also reveal the necessary overhead introduced by these two services in our implementation.