• Proceedings of the Korea Database Society Conference
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• 1994.09a
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• pp.105-129
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• 1994

The information system of corporations are facing a new environment expressed by miniaturization, decentralization and Open System. It is therefore of utmost importance for corporations to adapt flexibly th such new environment by providing for corresponding changes to their existing information systems. The objectives of this study are to identify this new environment faced by today′s information system and develop effective methods for data resource management under this new environment. In this study, it is assumed that the new environment faced by information systems can be specified as Distributed Computing Environment, and in order to achieve such system, presents Client/server architecture as its representative computing structure, This study defines Client/server architecture as a computing architecture which specialize the fuctionality of the client system and the server system in order to have an application distribute and perform cooperative processing at the best platform. Furthermore, from among the five structures utilized in Client/server architecture for distribution and cooperative processing of application between server and client this study presents two different data management methods under the Client/server environment; one is "Remote Data Management Method" which uses file server or database server and. the other is "Distributed Data Management Method" using distributed database management system. The result of this study leads to the conclusion that in the client/server environment although distributed application is assumed, the data could become centralized (in the case of file server or database server) or decentralized (in the case of distributed database system) and the data management method through a distributed database system where complete responsibility and powers with respect to control of data used by the user are given not only is it more adaptable to modern flexible corporate environment, but in terms of system operation, it presents a more efficient data management alternative compared to existing data management methods in terms of cutting costs.

• Journal of Korea Spatial Information System Society
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• v.6 no.2 s.12
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• pp.51-62
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• 2004

Recently, the location-based service for moving customers is becoming one of the most important service in mobile communication area. For moving object applications, there are lots of update operations and such update loads are concentrated on some particular area unevenly. The primary processing of LBS application is spatio-temporal range queries. To improve the throughput of spatio-temporal range queries, the time of disk I/O in query processing should be reduced. In this paper, we adopt non-uniform two-level grid index structures of GALIS architecture,which are designed to minimize update operations. We propose query scheduling technique using spatial relationship and time relationship and a combined spatio-temporal query processing method using time zone concepts to improve the throughput of query processing. Some experimental results are shown for range queries with different query range to show the performance tradeoffs of the proposed methods.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.208-217
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• 2008

Sensors have a function to gather environment-related information operating by small-size battery in sensor networks. The issue related with energy is still an important in spite of the recent advancements in micro-electro-mechanical-system(MEMS) related techology. Generally it is assumed that replacement or rechargement of battery power in sensor is not feasible and a message send operation may spend at least 1000 times battery than a local operation. Thus, there have been several kinds of research efforts to lessen the number of unnecessary messages by maintaining the information of the other neighboring(or all) sensors. In this paper, we propose an index structure based on parent-children relationship to the purpose. Namely, parent node gathers the set of location information and MBA per child. It's named PH and may allow to process the range query with higher accurate and small size information. Through extensive experiments, we show that our index structure has better energy consumption.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.9
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• pp.608-614
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• 2006

The popularization of high-speed networks and the innovation of high-performance hardware/servers have enlarged the role of large-scale, highly distributed IT infrastructure. Though many criteria on the assessment of IT infrastructure can be considered, the survivability assessment is treated as the most important one due to the essential role as an infrastructure. While assessing the survivability of some given IT infrastructures, we can not only choose the best one among them but also improve their survivability by modifying their structure and security policies. In this paper, we propose a DMKB-based assessment system on the survivability of IT infrastructures, where DMKB is a kind of database which provides the known vulnerabilities and defense mechanism for many system components.

• Journal of KIISE:Databases
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• v.37 no.4
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• pp.203-208
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• 2010

This paper deals with an efficient index scheduling technique based on Hilbert curve and MBR for k-NN query in a single wireless broadcast channel environment. Previous works have two major problems. One is that they need a long time to process queries due to the back-tracking problem. The other is that they have to download too many spatial data since they can not reduce search space rapidly. Our proposed method broadcasts spatial data based on Hilbert curve order where a distributed index table is also broadcast with each spatial data. Each entry of index table represents the MBR which groups spatial data. By predicting the unknown location of spatial data, our proposed index scheme allows mobile clients to remove unnecessary data and to reduce search space rapidly. As a result, our method gives the decreased tuning time and access latency.

• Journal of Korea Spatial Information System Society
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• v.8 no.2 s.17
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• pp.75-89
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• 2006

LBS (Location-Based Service) systems have become a serious subject for research and development since recent rapid advances in wireless communication technologies and position measurement technologies such as global positioning system. The architecture named the GALIS (Gracefully Aging Location Information System) has been suggested which is a cluster-based distributed computing system architecture to overcome performance losses and to efficiently handle a large volume of data, at least millions. The GALIS consists of SLDS and LLDS. The SLDS manages current location information of moving objects and the LLDS manages past location information of moving objects. In this thesis, we implement a monitoring technique for the GALIS prototype, to allow dynamic load balancing among multiple computing nodes by keeping track of the load of each node in real-time during the location data management and spatio-temporal query processing. We also propose a buffering technique which efficiently manages the query results having overlapped query regions to improve query processing performance of the GALIS. The proposed scheme reduces query processing time by eliminating unnecessary query execution on the overlapped regions with the previous queries.

• Journal of Korea Spatial Information System Society
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• v.8 no.2 s.17
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• pp.91-107
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• 2006

To handling the extreme situation that must manage positional information of a very large volume, at least millions of moving objects. A cluster-based sealable distributed computing system architecture, called the GALIS which consists of multiple data processors, each dedicated to keeping records relevant to a different geographical zone and a different time zone, was proposed. In this paper, we proposed a valid time management and time-zone shifting scheme, which are essential in realizing the long-term location data subsystem of GALIS, but missed in our previous prototype development. We explain how to manage valid time of moving objects to avoid ambiguity of location information. We also describe time-zone shifting algorithm with three variations, such as Real Time-Time Zone Shifting, Batch-Time Zone Shifting, Table Partitioned Batch-Time Zone Shifting, Through experiments related with query processing time and CPU utilization, we show the efficiency of the proposed time-zone shifting schemes.

• The KIPS Transactions:PartD
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• v.8D no.3
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• pp.211-220
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• 2001

A planning agent supporting customers plays a distinguished role in internet marketplaces. Although several internet marketplaces have been built with the maturity of tools based on internet and distributed technologies, there has been no actual study up to now with respect to the implementation of the planning agent. This paper describes the design and implementation of an XML-based planning agent for internet marketplaces. Since implementing internet marketplaces encounter problems similar to those in other fields such as multidatabase or workflow management systems, we first compare those features. Next we identify functions and roles of the planning agent. The planning agent is implemented using COM+, ASP, and XML, and demonstrated using real data used in an existing system.

• The Journal of Information Technology and Database
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• v.1 no.2
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• pp.37-52
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• 1994

오늘날의 정보시스템 구축 방향은 대형 컴퓨터를 중심으로 수많은 단말기를 연결한 수직형네트워크 시스템에서 다운사이징과 네트워크 기술이 결합하여 분산적으로 자료를 처리하는 클라이언트/서버 시스템 구축으로 변화하고 있다. 본 연구는 모든 단말기를 통제하는 대형 컴퓨터를 운영하는 전산망에서 클라이언트/서버 전산망으로 전환하는 하나의 사례연구를 통하여 구축환경변화, 시스템구성, 경영환경변화를 분석함으로써 클라이언트/서버 시스템의 성공적인 사례를 제시하는 것이다. 클라이언트/서버 시스템으로 변환하기전에 재개발할 시스템의 목표와 방향을 설정하기 위해서 벤치마킹을 실시하였고, 이의 결과를 바탕으로 경영업무의 프로세스를 재설계 하였다. 그리고 기업의 내부와 외부자료에 관한 표준화를 실시하였다. 정보기술 투자의 경제성과 경쟁우위 확보를 위하여 클라이언트/서버 시스템을 구현하게 되었으며 판매물류, 생산물류, 그리고 재무회계에 관한 경영지원시스템으로 구성되는 종합물류시스템 이외에 영업소에 관련된 영업정보시스템과 자동창고시스템이 컴퓨터 네트워크와 관련해서 시스템을 구성하였다. 구성 전략 촛점은 리엔지니어링, 다운사이징, 그리고 벤치마킹이었다. 시스템을 재개발한 후 업무의 계획, 진행, 분석, 감리등에 관한 체계적 업무흐름이 정착될 정도로 변화하였으며, 통신방식의 확대 및 다양화로 의사소통의 원활화와 타 관련업무와 연계처리, 그리고 부서들 상호간에 정보를 공유할 수 있었다. 또한 정보기술에 의한 업무처리를 기본으로 하는 기능적 태도로 인하여 관리자와 실무자의 업무운영에 관한 사고와 의식이 변화하였다. 따라서 매출액의 증가와 종업원수가 감소되었다.

• Journal of KIISE:Information Networking
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• v.29 no.3
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• pp.286-298
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• 2002

The Remote Procedure Call(RPC) has been traditionally used for Inter Process Communication(IPC) among precesses in distributed computing environment. As distributed applications have been complicated more and more, the Mobile Agent paradigm for IPC is emerged. Because there are some paradigms for IPC, researches to evaluate and compare the performance of each paradigm are issued recently. But the performance models used in the previous research did not reflect real distributed computing environment correctly, because they did not consider the evacuation elements for providing security services. Since real distributed environment is open, it is very vulnerable to a variety of attacks. In order to execute applications securely in distributed computing environment, security services which protect applications and information against the attacks must be considered. In this paper, we evaluate and compare the performance of the Remote Procedure Call with that of the Mobile Agent in IPC paradigms. We examine security services to execute applications securely, and propose new performance models considering those services. We design performance models, which describe information retrieval system through N database services, using Petri Net. We compare the performance of two paradigms by assigning numerical values to parameters and measuring the execution time of two paradigms. In this paper, the comparison of two performance models with security services for secure communication shows the results that the execution time of the Remote Procedure Call performance model is sharply increased because of many communications with the high cryptography mechanism between hosts, and that the execution time of the Mobile Agent model is gradually increased because the Mobile Agent paradigm can reduce the quantity of the communications between hosts.