• Journal of Computing Science and Engineering
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• 제3권1호
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• pp.27-58
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• 2009

Aggregation join queries are an important class of queries over data streams. These queries involve both join and aggregation operations, with window-based joins followed by an aggregation on the join output. All existing research address join query optimization and aggregation query optimization as separate problems. We observe that, by putting them within the same scope of query optimization, more efficient query execution plans are possible through more versatile query transformations. The enabling idea is to perform aggregation before join so that the join execution time may be reduced. There has been some research done on such query transformations in relational databases, but none has been done in data streams. Doing it in data streams brings new challenges due to the incremental and continuous arrival of tuples. These challenges are addressed in this paper. Specifically, we first present a query processing model geared to facilitate query transformations and propose a query transformation rule specialized to work with streams. The rule is simple and yet covers all possible cases of transformation. Then we present a generic query processing algorithm that works with all alternative query execution plans possible with the transformation, and develop the cost formulas of the query execution plans. Based on the processing algorithm, we validate the rule theoretically by proving the equivalence of query execution plans. Finally, through extensive experiments, we validate the cost formulas and study the performances of alternative query execution plans.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2007년도 Proceedings of ISRS 2007
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• pp.101-104
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• 2007

Efficient Query processing and optimization are critical for reducing network traffic and decreasing latency of query when accessing and manipulating sensor data of large-scale sensor networks. Currently it has been studied in sensor database projects. These works have mainly focused on in-network query processing for sensor networks and assumes homogeneous sensor networks, where each sensor network has same hardware and software configuration. In this paper, we present a framework for efficient query processing over heterogeneous sensor networks. Our proposed framework introduces query processing paradigm considering two heterogeneous characteristics of sensor networks: (1) data dissemination approach such as push, pull, and hybrid; (2) query processing capability of sensor networks if they may support in-network aggregation, spatial, periodic and conditional operators. Additionally, we propose multi-query optimization strategies supporting cross-translation between data acquisition query and data stream query to minimize total cost of multiple queries. It has been implemented in WSN middleware, COSMOS, developed by ETRI.

• 디지털콘텐츠학회 논문지
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• 제8권4호
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• pp.541-546
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• 2007

많은 양의 연속적인 스트림 데이터를 대상으로 하는 연속적인 질의처리의 경우는 전통적 방식의 요구구동형 질의처리 방식이 적합하지 않다. 본 논문에서는 자료구동형 방식을 도입하여 질의를 처리함으로써 스트림 데이터에 알맞은 질의처리 기법을 제안하고 질의계획의 구조와 질의실행 방식을 설명하였다. 제안된 질의처리 기법은 다중질의 처리가 가능하며, 질의 간에 공유가 가능하게 한다. 또한 부분질의의 실행결과가 저장됨으로써 실행시간을 단축할 수 있다. 본 질의처리 모델에 XML 데이터와 XQuery 질의를 적용하였다.

• 한국전자거래학회지
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• 제7권3호
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• pp.21-48
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• 2002

ebXML is the international technical framework specification that enables Internet-based B2B electronic business using XML, It was standardized by UN/CEFACT and OASIS on May 2001. Registry and Repository is the core of ebXML. It supports registry services which is composed of object management service and object query management service. The object management service manages the object's life cycle and the object query management service provides a mechanism to approach metadata of stored objects. Up to now, implementations of ebXML Registry object query management system don't support full functions of the specification completely. We implemented all the functions of ebXML Registry Service Specification vl.0. This system supports Browse ＆ Drilldown Query, Filter Query, SQL Query, and Object Retrieval Query services. And it also supports Content-based Query service which is not specified in the ebXML RS specification. The Content-based Query service is a repository service which makes it possible In pose content based queries of repository items and which will be specified on the RS specification v2.0.

• 한국콘텐츠학회논문지
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• 제8권1호
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• pp.290-299
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• 2008

본 논문에서는 하이브리드 공간 DBMS에서 질의 분류를 이용한 최적화 기법을 제안한다. 제안 기법은 질의에 이용되는 데이터의 위치에 따라 메모리 질의, 디스크 질의, 하이브리드 질의로 분류하여 처리한다. 특히, 하이브리드 질의의 경우에는 실체화 뷰의 사용률을 높이기 위해 실체화 뷰 생성 조건과 사용자 질의 조건을 비교하여 술어를 분할하는 메커니즘을 적용한다. 또한 질의를 최적화하기 위해 분류된 질의의 비용 계산 결과를 이용하여 최소 비용의 데이터 접근 경로를 선택할 수 있는 데이터 접근 경로 선택 알고리즘을 제안한다. 제안 기법은 대용량 데이터 관리와 빠른 응답 속도를 동시에 만족하는 하이브리드 공간 DBMS의 성능을 기존의 디스크 기반 공간 DBMS보다 최소 20%에서 최대 50%의 성능 향상을 보인다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제16권9호
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• pp.3087-3103
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• 2022

Nearest neighbor query in location-based services has become a popular application. Aiming at the shortcomings of the privacy protection algorithms of traditional ciphertext nearest neighbor query having the high system overhead because of the usage of the double Hilbert curves and having the inaccurate query results in some special circumstances, a privacy protection algorithm of ciphertext nearest neighbor query which is based on the single Hilbert curve has been proposed. This algorithm uses a single Hilbert curve to transform the two-dimensional coordinates of the points of interest into Hilbert values, and then encrypts them by the order preserving encryption scheme to obtain the one-dimensional ciphertext data which can be compared in numerical size. Then stores the points of interest as elements composed of index value and the ciphertext of the other information about the points of interest on the server-side database. When the user needs to use the nearest neighbor query, firstly calls the approximate nearest neighbor query algorithm proposed in this paper to query on the server-side database, and then obtains the approximate nearest neighbor query results. After that, the accurate nearest neighbor query result can be obtained by calling the precision processing algorithm proposed in this paper. The experimental results show that this privacy protection algorithm of ciphertext nearest neighbor query which is based on the single Hilbert curve is not only feasible, but also optimizes the system overhead and the accuracy of ciphertext nearest neighbor query result.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2003년도 춘계종합학술대회
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• pp.658-661
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• 2003

멀티미디어 데이터베이스 시스템에서는 멀티미디어 데이터를 질의하고 질의 결과를 어떻게 프리젠테이션 할 것인가에 대한 연구는 매우 중요하다. 또한 질의의 결과를 다양한 응용에서 사용하기 위해서는 보다 일반화된 형태로 질의결과를 제공해야 할 필요가 있다. 본 논문에서는 멀티미디어 페이퍼베이스 시스템에서 멀티미디어 프리젠테이션을 지원하는 MMSQL 질의처리기를 설계하고 구현하였다. 또한 질의 결과 프리젠테이션을 보다 일반화된 형태인 SMIL문서로 제공하도록 함으로써 질의 결과를 다양한 응용에서 쉽게 사용할 수 있도록 하였다.

• Journal of Information Processing Systems
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• 제14권2호
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• pp.396-417
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• 2018

GR-tree and query aggregation techniques have been proposed for spatial query processing in conventional spatial query processing for wireless sensor networks. Although these spatial query processing techniques consider spatial query optimization, time query optimization is not taken into consideration. The index reorganization cost and communication cost for the parent sensor nodes increase the energy consumption that is required to ensure the most efficient operation in the wireless sensor node. This paper proposes itinerary-based R-tree (IR-tree) for more efficient spatial-temporal query processing in wireless sensor networks. This paper analyzes the performance of previous studies and IR-tree, which are the conventional spatial query processing techniques, with regard to the accuracy, energy consumption, and query processing time of the query results using the wireless sensor data with Uniform, Gauss, and Skew distributions. This paper proves the superiority of the proposed IR-tree-based space-time indexing.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2010년도 추계학술대회
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• pp.691-694
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• 2010

센서 노드에서 수집되는 데이터는 지속적으로 삽입되는 스트림 데이터이기 때문에 효율적인 사용자 질의 처리를 위하여 노드별로 질의 색인을 구축해야 한다. 노드에서 최소 크기의 질의 색인을 구축하기 위해서는 질의 색인에 삽입되는 질의 조건을 수를 줄여야 할 필요가 있다. 이 논문에서는 삽입되는 질의 조건의 수를 줄이기 위하여 다차원 데이터 색인을 이용한 질의 조건 배분 기법에 대하여 제안한다.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.715-717
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• 2003

Some previous works for nearest neighbor (NN) query processing technique can treat a case that query/data are both moving objects. However, they cannot find exact result owing to vagueness of criterion. In order to escape their limitations and get exact result, we propose new NN query techniques, exact CTNN (continuous trajectory NN) query, approximate CTNN query, and dynamic CTNN query. These are all superior to pervious works, by reducing of number of calculation, considering of trajectory information, and using of continuous query concept. Using these techniques, we can solve any situations and types of NN query in location-aware environment.