• Journal of Industrial Technology
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• v.10
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• pp.73-76
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• 1990

본 논문은 대용량 주기억장치를 갖는 컴퓨터 상에서 효율적으로 수행 될 수 있는 외부 합병정렬 방법에 대하여 기술한다. 제시된 정렬 방법은 주기억 장치의 용량이 정렬될 화일 크기의 제곱근보다 크다는 조건하에서, 주기억 장치를 최대로 이용하여 외부 합병정렬에 소요되는 외부 합병의 횟수를 최소화 함으로써 외부 합병정렬의 성능에 가장 큰 영향을 미치는 입출력 시간을 크게 줄일수 있음을 보였다.

• The KIPS Transactions:PartD
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• v.9D no.4
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• pp.579-586
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• 2002

This paper propose an efficient algorithm for mining association rules in the large main memory systems. To do this, the paper attempts firstly to extend the conventional algorithms such as DHP and Partition in order to be compatible to the large main memory systems and proposes secondly an algorithm to improve Partition algorithm by applying the techniques of the hash table and the bit map. The proposed algorithm is compared to the extended DHP within the experimental environments and the results show up to 65% performance improvement in comparison to the expanded DHP.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.153-156
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• 2004

위치기반 서비스 시스템에서 주 요구사항은 사용자의 실시간 위치 정보 검색과 질의에 대한 빠른 응답시간이다. 그러나 기존의 위치기반서비스 시스템에서 저장장치로 사용하는 디스크 기반 데이터베이스 시스템은 빈번한 디스크 I/O로 인해 발생하는 질의응답에 대한 시간지연으로 이러한 요구사항을 만족시키지 못한다. 또한 주기억장치 데이터베이스 시스템은 한번에 주기억장치에 적재할 수 있는 양이 제한되어 있기 때문에 대용량의 공간 데이터를 처리하는데 문제가 있다. 본 논문에서는 위치기반서비스를 위하여 위치 정보 데이터의 다단계 저장 관리를 통해 LBS 플랫폼에서 실시간 서비스를 지원하는 하이브리드 저장 관리자를 제안한다. 하이브리드 저장 관리 시스템은 위치기반 서비스 시스템에서 대용량의 이동체 데이터의 효과적인 저장 및 관리를 위해 주기억장치 데이터베이스 관리시스템과 디스크 기반의 공간 데이터베이스 관리시스템을 통합한 구조를 가진다. LBS 플랫폼에서 빠른 응답을 필요로 하고 자주 사용되는 데이터는 메모리 기반의 데이터베이스에 관리를 하고, 사용 빈도가 적은 데이터는 디스크 기반의 데이터베이스에 관리하는 하이브리드 저장 관리자를 제시한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.10a
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• pp.109-112
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• 2000

이동 단말기 관리, 무인 항공 제어 시스템 둥의 시스템에서는 검색 대상의 정보(위치, 여러 가지 상태등)가 시시각각으로 빠르게 변화하므로 현재의 상태를 정확히 파악하기 위하여 많은 양의 자료 검색, 변경 요청이 빈번히 발생한다. 이와 같은 시스템에서의 상태 정보 검색은 자료의 효용성이 사라지기 전에 이루어져야 하므로 디스크 I/O가 많은 디스크 상주형 데이터베이스로는 한계점을 안고 있다. 또한 빠른 검색을 지원할 수 있는 주기억장치 상주형 데이터베이스로는 다량의 데이터를 저장해야 하는 어려움을 안고 있다. 본 논문에서는 위와 같은 실시간 검색 기능과 대용량 자료 저장의 2가지 요구 사항을 만족시키기 위한 내장형 주기억장치 저장 시스템을 개발하였다.

• The KIPS Transactions:PartD
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• v.11D no.1
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• pp.11-22
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• 2004

As random access memory chip gets cheaper, it becomes affordable to realize main memory-based database systems. Consequently, reducing cache misses emerges as the most important issue in current main memory databases, in which CPU speeds have been increasing at 60% per year, compared to the memory speeds at 10% per you. In this paper, we design and implement a main-memory database system for real-time mobile GIS. Our system is composed of 5 modules： the interface manager provides the interface for PDA users； the memory data manager controls spatial and non-spatial data in main-memory using virtual memory techniques； the query manager processes spatial and non-spatial query : the index manager manages the MR-tree index for spatial data and the T-tree index for non-spatial index : the GIS server interface provides the interface with disk-based GIS. The MR-tree proposed propagates node splits upward only if one of the internal nodes on the insertion path has empty space. Thus, the internal nodes of the MR-tree are almost 100% full. Our experimental study shows that the two-dimensional MR-tree performs search up to 2.4 times faster than the ordinary R-tree. To use virtual memory techniques, the memory data manager uses page tables for spatial data, non- spatial data, T-tree and MR-tree. And, it uses indirect addressing techniques for fast reloading from disk.

• The KIPS Transactions:PartD
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• v.12D no.4 s.100
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• pp.543-552
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• 2005

As random access memory chip gets cheaper, it becomes affordable to realize main memory-based database systems. The disk-based spatial indexing techniques, however, cannot direct apply to main memory databases, because the main purpose of disk-based techniques is to reduce the number of disk accesses. In main memory-based indexing techniques, the node access time is much faster than that in disk-based indexing techniques, because all index nodes reside in a main memory. Unlike disk-based index techniques, main memory-based spatial indexing techniques must reduce key comparing time as well as node access time. In this paper, we propose an efficient spatial index structure for main memory-based databases, called Tmr-tree. Tmr-tree integrates the characteristics of R-tree and T-tree. Therefore, Nodes of Tmr-tree consist of several entries for data objects, main memory pointers to left and right child, and three additional fields. First is a MBR of a self node, which tightly encloses all data MBRs (Minimum Bounding Rectangles) in a current node, and second and third are MBRs of left and right sub-tree, respectively. Because Tmr-tree needs not to visit all leaf nodes, in terms of search time, proposed Tmr-tree outperforms R-tree in our experiments. As node size is increased, search time is drastically decreased followed by a gradual increase. However, in terms of insertion time, the performance of Tmr-tree was slightly lower than R-tree.

• Journal of KIISE:Computer Systems and Theory
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• v.28 no.5
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• pp.213-217
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• 2001

Excessive memory buffer requirement in continuous media playback is a serious impediment of wide spread usage of on-line multimedia service. Skewed access frequency of available video files provides an opportunity of re-using the date blocks which has been loaded by one session for later usage. We present novel algorithm which minimizes the buffer requirement in multiple sessions of multimedia playbacks. In continuous media playback originated from the disk, a certain amount of memory buffer is required to synchronize asynchronous disk. Read operation and synchronous playback operation. As aggregate playback bandwodth increases, larger amount of buffer needs to be allocated for this synchronization purpose. The focus of this work is to study the asymptotic behavior of the synchronization buffer requirement and to develop an algorithm coping with this excessive buffer requirement under bandwidth congestioon. We argue that in a large scale continuous media server, it may not be necessary to read the blocks for each session directly from the disk. The beauty of our work lies in the fact that it dynamically adapts to disk utilization of the server and finds the optimal way of servicinh the individual sessions while minimizing the overall buffer space requirement. Optimality of the proposed algorithm is shown by proof. The effectiveness and performance of the proposed scheme is examined via simulation.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.91-98
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• 2004

DHP mining association rules algorithm maintains previously independent direct hash table to reduce the sire of hash tree containing the frequency number of each candidate large itemset. It performs pruning by using the direct hash table when the hash tree is constructed. The mort large the size of direct hash table increases, the higher the effort of pruning becomes. Especially, the effect of pruning in phase 2 which generate 2-large itemsets is so high that it dominates the overall performance of DHP algorithm. So, following the speedy trends of producing VLM(Very Large Memory) systems, extreme increment of direct hash table size is being tried and one of those trials is perfect hash table in phase 2. In case of using perfect hash table in phase 2, we found that some rearrangement of DHP algorithm got about 20% performance improvement compared to simply ｜H$_2$｜ reconfigured DHP algorithm. In this paper, we examine the feasibility of perfect hash table in phase 2 and propose PHP algorithm, a rearranged DHP algorithm, which uses the characteristics of perfect hash table sufficiently, then make an analysis on the results in experimental environment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.18 no.5
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• pp.730-738
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• 1993

This paper proposes a dynamic formatting method for processing large amounts of document in a device independent manner. And it is very useful for cross-referencing among pages in a single document and for presenting multiple pages simultaneously. The method can be applied usefully to hypertext's application such as establishing a link and a cross-reference among pages in a multiple document. We implemented an electronic publishing system of WYSIWYG type using X window system and Motif graphical user interface.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.4 no.1
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• pp.28-37
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• 1993

The future Personal Communication Service(PCS) is the total personal information communication service to satisfy the importance of information in a highly information - oriented society. Compared with the conventional communication method, it is necessary to provide considerable intelligence to the commu- nication network in order to implement the PCS which guarantees the mobility of each individual. Consequen- tly, the PCS needs a fast large database system which stores the information of each individual. To achieve this goal, this paper presents the parallel implementation of deductive database systems as a main - memory database system.