• Proceedings of the Korean Information Science Society Conference
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• 2003.04a
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• pp.737-739
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• 2003

최근에 이동 객체의 위치를 추적하는 기술은 여러 응용 분야에서 중요성이 증대되고 있다. 그러나 지속적으로 움직이는 이동 객체의 위치를 추적하기 위해서는 매우 많은 수의 인덱스 변경 연산을 수행하여야 하므로 R-트리와 같은 전통적인 공간 인덱스 구조로는 처리하기 어렵다. 이러한 문제를 해결하기 위하여 객체의 움직임을 간단한 선형 함수로 가정하여 색인하는 연구들이 있어왔지만, 실제 응용에서는 객체의 움직임이 매우 복잡하므로 이러한 방법을 이용하기 적합하지 않다. 본 논문에서는 복잡한 움직임을 가지는 객체를 효율적으로 색인하기 위한 R-트리의 지연 갱신 기법을 제안한다. 이 기법은 객체가 이동할 때마다 트리의 구조를 변경하지 않고, 객체가 이전에 속해 있던 R-트리의 MBR(Minimum Bounding Rectangle)을 벗어날 때만 트리의 구조를 변경하므로 R-트리의 갱신 연산 비용을 크게 줄일 수 있다. 뿐만 아니라, 기본적인 R-트리의 구조와 연산을 그대로 이용하므로 다양한 R-트리 변종 트리에서도 쉽게 적용이 가능하고, R-트리를 이용하여 이미 구축되어 있는 다양한 응용 환경에 쉽게 이용할 수 있다.

• Journal of KIISE:Databases
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• v.27 no.4
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• pp.651-662
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• 2000

멀티미디어 데이터베이스에서 k-최근접 질의는 가장 일반적이며, 비공간 검색 조건이 포함된 경우가 많다. 현재까지 이러한 질의를 위한 여러 기법 중에서 Hjaltason과 Samet이 제안한 점증적 최근접 알고리즘에 가장 유용하다고 알려져 있다. 질의 처리를 위해 상위 연산자가 k보다 많은 객체를 요구할 때, 이 알고리즘은 처음부터 질의를 재실행하지 않고 다음 객체를 전달할 수 있기 때문이다. 그런데, 이 알고리즘에서 사용하는 R-트리는 결국에는 비공간 검색조건을 만족시키지 않을 투플 후보들을 부분적으로 제거할 수가 없기 때문에 비효율적이다. 본 논문에서 우리는 이 알고리즘을 보완한 RS-트리 기반 점증적 최근접 알고리즘을 제안한다. RS-트리는 R-트리와, 그 보조 트리로서 계층적 시스니쳐 파일을 기반으로 하는 S-트리로 구성된다. S-트리는 R-트리를 탐색하는 과정에서 많은 불필요한 투플을 제거하는 역할을 수행한다. 본 논문에서는 실험을 통해 RS-트리가 Hjaltason과 Samet의 알고리즘의 성능을 향상시킬 수 있음을 보인다.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.651-665
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• 2003

To reduce cache misses emerges as the most important issue in today's situation of main memory databases, in which CPU speeds have been increasing at 60% per year, and memory speeds at 10% per year. Recent researches have demonstrated that cache-conscious index structure such as the CR-tree outperforms the R-tree variants. Its search performance can be poor than the original R-tree, however, since it uses a lossy compression scheme. In this paper, we propose alternatively a cache-conscious version of the R-tree, which we call MR-tree. The MR-tree propagates node splits upward only if one of the internal nodes on the insertion path has empty room. Thus, the internal nodes of the MR-tree are almost 100% full. In case there is no empty room on the insertion path, a newly-created leaf simply becomes a child of the split leaf. The height of the MR-tree increases according to the sequence of inserting objects. Thus, the HeightBalance algorithm is executed when unbalanced heights of child nodes are detected. Additionally, we also propose the CCMR-tree in order to build a more cache-conscious MR-tree. Our experimental and analytical study shows that the two-dimensional MR-tree performs search up to 2.4times faster than the ordinary R-tree while maintaining slightly better update performance and using similar memory space.

• 축산식품과학과 산업
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• v.12 no.2
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• pp.63-70
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• 2023

• 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.

• Proceedings of the Korean Information Science Society Conference
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• 2006.06d
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• pp.28-30
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• 2006

스트리밍 서비스는 인터넷 트래픽의 많은 부분을 차지할 정도로 인기 있는 서비스가 되었고, 확장성을 위해 P2P기반의 스트리밍 서비스가 제안되었다. P2P기반 스트리밍 환경은 빈번한 피어들의 떠남과 합류가 일어난다. 이러한 멀티캐스트 그룹의 변화에 대처하기 위해서 다중 멀티캐스트 트리가 제안되었다. 이는 중복성을 통해 멀티캐스트 그룹의 변화에 따른 영향을 줄였다. 하지만 노드의 능력 차이를 고려하지 않았기 때문에 트리가 길어지고, 불안정해질 수 있다. 이를 위해 본 논문은 노드의 능력을 고려한 내구적 멀티캐스트 트리 생성 기법(R-CAT)을 제시하여 우수 노드를 트리의 상층부에 위치시킴으로써 트리의 길이를 줄이고 트리 상층부의 안정화 문제를 해결할 수 있다. 또한 제시한 기법의 유효성을 증명하기 위해 기존의 SplitStream을 확장해서 R-CAT을 구현, 비교 검증한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1250-1256
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• 2004

The movement of continuously changing positions should be stored and indexed for querying current and past positions. A simple extension of the original R-tree to add time as another dimension, called 3D R-tree, does not handle current position queries and does not address the problem of low space utilization due to high overlap of index nodes. In this paper, 1 propose the dynamic splitting policy for improving the 3D R-tree in order to improve space utilization of split nodes. 1 also extend the original 3D R-tree by introducing a new tagged index structure for being able to query the current and past positions of moving objects. 1 found out that my extension of the original R-tree, called the tagged dynamic 3DR-tree, outperforms both the 3D R-tree and 75-tree when querying current and past position.

• The KIPS Transactions:PartA
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• v.13A no.2 s.99
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• pp.147-156
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• 2006

Recently, streaming service accounts for large part of internet traffic and it is becoming the most popular service. Because of P2P's scalability, P2P-based streaming system is proposed. There are frequent leave and join of a node. To overcome the group dynamics, Multiple Multicast Trees Methods were suggested. However, since they did not consider discrepancy in peers' capacity, it may cause the trees to be long and unstable. So we suggest Resilient Capacity-Aware Multicast Tree construction scheme (R-CAT) that promotes superior peer to upper position in the tree and construct more stable and short multicast trees. By simulation we can show that R-CAT cost more overhead packets for tree joining process, but it reduce the end-to-end delay of the resulting tree and the number of packets lost during the node joining and leaving processes much more than SplitStream.

• Journal of KIISE:Databases
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• v.31 no.3
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• pp.261-273
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• 2004

Advances in information and communication technologies have been creating new classes of applications in the area of databases. For example, in moving object databases, which track positions of a lot of objects, or stream databases, which process data streams from a lot of sensors, data Processed in such database systems are usually changed very rapidly and continuously. However, traditional database systems have a problem in processing these rapidly and continuously changing data because they suppose that a data item stored in the database remains constant until It is explicitly modified. The problem becomes more serious in the R-tree, which is a typical index structure for multidimensional data, because modifying data in the R-tree can generate cascading node splits or merges. To process frequent updates more efficiently, we propose a novel update technique for the R-tree, which we call the leaf-update technique. If a new value of a data item lies within the leaf MBR that the data item belongs, the leaf-update technique changes the leaf node only, not whole of the tree. Using this leaf-update manner and the leaf-access hash table for direct access to leaf nodes, the proposed technique can reduce update cost greatly. In addition, the leaf-update technique can be adopted in diverse variants of the R-tree and various applications that use the R-tree since it is based on the R-tree and it guarantees the correctness of the R-tree. In this paper, we prove the effectiveness of the leaf-update techniques theoretically and present experimental results that show that our technique outperforms traditional one.

• The Journal of the Korea Contents Association
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• v.7 no.7
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• pp.11-23
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• 2007

Applications involving moving objects require index structures to handle frequent updates of objects' locations efficiently. Several methods to index the current, the past and the future positions of moving objects have been proposed for the applications. Most of them are based on R-tree like index structures. Some researches have made efforts to improve update performance of R-trees that are actually focused on query performance. Even though the update performance is improved by researchers' efforts, the overhead and immaturity of concurrency control algorithms of R-trees makes us hesitate to choose them for moving objects. In this paper, we propose an update efficient indexing method that can be applicable for indexing the past, the current and the future locations. The proposed index is based on B+-Trees and Hilbert curve. We present an advanced Hilbert curve that adjusts automatically the order of Hilbert curve in subregions according to the data distribution and the number of data objects. Through empirical studies, we show that our strategy achieves higher response time and throughput.