Browsing by Author "Lo, W"

Now showing 1 - 9 of 9

A fault-tolerant object service on CORBA
(1997)
Sheu, GW
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Chang, YS
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Liang, DR
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Yuan, SM
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Lo, W
There are more and more COSS (Common Object Service Specification) on CORBA (Common Object Request Broker Architecture) that is announced by the OMG (Object Management Group), bur no common specification about fault-tolerance exists now. In this paper, we propose a ''warm stand-by'' replication approach. When an object (primary object) is invoked, it will invoke a secondary object, and the primary object will log the messages and checkpoint the state to the secondary object periodically. If the primary object fails, the secondary object can take over by way of client executing a few operations to change secondary object's mode to primary's. Following the style of COSS, we define four interfaces and provide class implementations that can help programmers write programs with fault-tolerant capability. The whole model has been implemented on Orbix, which is a full implementation of CORBA specification.
A new development environment for an event-based distributed system
(2003-08-01)
Hsiao, TY
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Perng, NC
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Lo, W
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Chang, YS
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Yuan, SM
The rapid growth of data exchange on the Internet has created many critical problems that require an answer. Traditional data exchange systems based on client/server communication models are less scalable and incur especially high maintenance cost in the data exchange domain. For these reasons, many researchers have switched their interest to asynchronous communication models. Although Message-Oriented Middleware (MOM) is a middle-tier infrastructure that links operating systems and applications, such asynchronous communication APIs supported by middleware vendors are usually hard to use. For these reasons, in this study, we present a new development environment for asynchronous communication platforms which we term Ghostwriter. The keyword for our development environment is 'easy', that is, easy to,use, easy to develop, and easy to deploy. Therefore, many researchers have switched their interest to asynchronous communication models. In addition, learning about and implementing the functions of the asynchronous communication's clients in Ghostwriter environment is simple. Other benefits are a lower technical learning curve, help for concentrate on system design, has easily reusable components, and easily integrated applications. (C) 2003 Elsevier Science B.V. All rights reserved.
A new multi-search engine for querying data through an Internet search service on CORBA
(2000-09-01)
Chang, YS
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Yuan, SM
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Lo, W
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資訊工程學系
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Department of Computer Science
Search engines are important but generally far from ideal tools of the World Wide Web (WWW). Many researchers therefore prefer to use meta-brokers to construct multi-search engines (MSE). However, these have no uniform programming interfaces, which makes tying them with other search engines difficult. Moreover, for an application that needs a search service capability, querying them is difficult. To reduce that difficulty, we propose in this paper an Internet search service (ISS) based on common object request broker architecture (CORBA) that follows the style of common object service specification (COSS). We design a multi-search engine based on ISS, which we term Octopus. For a system developer, because of its uniformity of interface, Octopus easily ties with any search engine. Equally, for an application programmer, the ISS offers a clear interface for application programs to search for information or mine data from the Internet. We demonstrate our approach to designing multi-search engines through ISS by tying two search engine agents, Yahoo and Alta Vista, with Octopus and show how CORBA clients query them. Programmers may use this interface to construct their search engine agents or query a search engine agent in their applications. (C) 2000 Elsevier Science B.V. All rights reserved.
An Information Store and Retrieval Facility on CORBA
(2000)
Lo, W
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Chang, YS
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Chou, CL
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Sheu, RK
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Yuan, SM
In this paper, we propose an Information Storage and Retrieval Facility based on the CORBA. This facility provides information search, retrieval and storage service. To define these services, we referred the Z39.50 and defined a set of interfaces by CORBA IDL. In addition, other information storage respect services, such as information update, information update notify, and information version control etc., and more other services, such as initial service, close service, and search command forward and distribution etc., were provided in this facility. Based on this facility, programmer can add the capability of query Z39.50 server into applications and also can integrate various data sources and provide an uniform interface. Finally, we also implement an experimental library management system to verify our design.
Design and implementation of multi-threaded object request broker
(1998)
Chang, YS
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Lo, W
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Wang, CJ
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Yuan, SM
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Liang, DR
Distributed object-oriented computing model is the next logical step to develop distributed applications. In recent year, several object models have been proposed, such as COM/DCOM, CORBA, and JAVA Bean etc. In CORBA, which is announced by OMG, object request broker is a software bus to connect applications and object components. In addition, multi-threaded programming is a well-known technique to improve the performance of applications. In CORBA environment, clients can invoke the remote objects that are shared. If those objects are single-threaded it will affect the performance of system by the large distributed applications. In this paper we will depict in detail the design and implementation of multi-threaded object request broker based on the CORBA. Our ORE nas implemented atop Windows NT and underlying TCP protocol. Finally, we will compare our system's performance with IONA's Orbix, which is a well-known commercial product, in both one-way and two-way request.
From legacy RPC services to distributed objects
(1997)
Liang, KC
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Chu, WC
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Yuan, SM
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Lo, W
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交大名義發表
Remote Procedure Call (RPC) paradigm has successfully modeled several sophisticated client-server applications. It provides a simple and efficient way to develop distributed programs. The concept of RPC comes from procedure-based programming languages. As the object oriented technologies grow, the idea of invoking program entities on different address spaces also comes into the object oriented software development. The distributed object computing is the realization of this trend. This paper is intended to identify the motivations, the issues, and the design of translating RPC services into CORBA objects via reengineering processes. The conversion includes: converting RPC languages to CORBA IDL, converting RPC server implementation source codes to COBRA server object implementation source code, and converting RPC clients source codes to CORBA client object source code.
Nested transaction and concurrency control services on CORBA
(1997)
Liang, KC
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Yuan, SM
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Liang, D
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Lo, W
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交大名義發表
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.
The design and implementation of a multi-threaded object request broker
(2000-05-01)
Lo, W
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Chang, YS
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Yuan, SM
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Liang, D
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資訊工程學系
Multi-threaded programming is a well-known technique for improving the performance of applications. In a CORBA environment, clients can invoke shared remote objects. If these objects are single-threaded, the performance of the system in the large distributed applications is affected. This paper presents a detailed description of the design and implementation of a multi-threaded Object Request Broker (ORB) on CORBA. The ORE was implemented on top of Windows NT and the underlying TCP protocol. The system's performance in both one-way and two-way requests is compared with that of a well-known commercial product, the IONA Orbix.
Two-level web agent for limited accessibility
(1997)
Yeh, PJ
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Yuan, SM
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Lo, W
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交大名義發表
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資訊工程學系
Many problems frustrate WWW users that suffer limited accessibility to WWW resources, and therefore we propose a 2-level agent architecture trying to solve them. The agent consists of 2 parts: the local agent interacts directly with end-users, while the remote agent interacts primarily with the public Internet. They together learn users' preferences, and help users find and filter information more efficiently: economically, and enjoyably. This paper introduces the concept of the 2-level agent, and investigates practical issues involved in further design.