• Journal of Korea Society of Industrial Information Systems
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• v.3 no.1
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• pp.153-164
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• 1998

적응 선채취 캐슁은 시스템 성능 향상을 위한 효율적인 기법이다. 이 논문에서는 객체지향 테이터베이스에서 디스크 참조에 대한 평균 서비스 기간을 감소시키기 새로운 캐슁 기법을 제안한다. 이전에 사용된 방법과는 달리 제안한 방법에서는 과거의 이력을 참조하여 채취 분기점을 탄력적으로 조정함으로써 캐슁의 효율을 향상시킨다. 다양한 질의로 시뮬레이션 한 결과 성능의 우수함을 확인할 수 있었다.

• The Transactions of the Korea Information Processing Society
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• v.6 no.1
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• pp.21-31
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• 1999

In this paper we study on an interface connection between spatial operators and temporal operators to support the unified operations for spationtemporal data. The integration development of the spatiotemporal operations will be defined as a common use of spatiotemporal relationship operators by spatiotemporal referencing macros. additionally we propose an integration algorithm of a history operator and temporal relationship operators. Then the proposed system will be implemented on the commercial GIS software and evaluated by examples of spatiotemporal query expressions. Here, our integration of spatial and temporal operators will provide spatiotemporal query expressions with a useful framework.

• The Transactions of the Korea Information Processing Society
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• v.5 no.7
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• pp.1671-1679
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• 1998

Temporal databases support an efficient hist0rical representation and operation for an object in the real world. Especiallv, temporal aggregates generate In additional by information by means of computations from objects that is valid at past as well as current time. It is one of important areas to serve to users as various type of aggregates as possible so that they enhance the overall system performance and efficiency. In this paper, we not only introduce temporal aggregate tree strategy as an efficient processing technique for given temporal aggregate query, but also analyze the ovemll processing cost and then evaluate its perfomlance.

• The KIPS Transactions:PartD
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• v.18D no.2
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• pp.111-122
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• 2011

These days RFID application has been developed rapidly. It has been applied to many business areas such as logistics and supply chains. The Electronic Product Code (EPC) Network Architecture, an open global standard, is proposed by EPCglobal for developing RFID enabled systems. People who want to obtain the product information which are master information and event information have to apply with EPC Network Architecture. However, EPCIS which has master information and event information has to be accessed base on each EPC. Therefore, there is lots of duplicate accessing to EPCIS because RFID application has to access the same EPCIS over again which makes all performance down in EPC Network. This paper proposes how to reduce access times to EPCIS using EPC grouping based on EPCIS address. We build EPC Network environment to experiment about performance of RFID application system and we prove the improvement of EPC Network. Our result shows the reducing the EPCIS communication time by maximum 99 percentages.

• The KIPS Transactions:PartD
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• v.12D no.1 s.97
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• pp.43-50
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• 2005

The Processing domains of spatio-temporal databases are divided into time-series databases for moving objects and sequence databases for discrete historical objects. Recently the selectivity estimation techniques for query optimization in spatio-temporal databases have been studied, but focused on query optimization in time-series databases. There wat no previous work on the selectivity estimation techniques for sequence databates as well. Therefore, we construct T-Minskew histogram for query optimization In sequence databases and propose a selectivity estimation method using the T-Minskew histogram. Furthermore we propose an effective histogram maintenance technique for food performance of the histogram.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.3
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• pp.509-516
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• 2008

Recently, the operator modules to control external devices are concerned about automatic management system to process continuously changed signals. These signals are the stream data of which characteristics are several numbers. a short report interval and asynchronous report time. It is necessary that the system brings about high accuracy and real time process for stream data. The typical queries of these systems consist of the current query to search the latest signal value, the snapshot query at a past time, the sliding window query from a past time to current. In this paper, we propose the efficient method to manage the above signals by using a file structured database in small-size operating systems. We also propose a query model to accommodate various queries including the sliding window query. The file database in the QNX adopts a delta version and a shared memory buffering method for the resource limit of a small storage and a low computing power.

• Journal of KIISE:Databases
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• v.34 no.1
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• pp.59-69
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• 2007

The trajectory of a tag in RFID system is represented as a interval that connects two spatiotemporal locations captured when the tag enters and leaves the vicinity of a reader. Whole trajectories of a tag are represented as a set of unconnected interval because the location of the tag which left the vicinity of a reader is unknown until it enters the vicinity of another reader. The problems are that trajectories of a tag are not connected. It takes a long time to find trajectories of a tag because it leads to searching the whole index. To solve this problem, we propose a technique that links two intervals of the tag and an index scheme called SLR-tree. We also propose a sharing technique of link information between two intervals which enhances space utilization of nodes, and propose a split policy that preserves shared-link information. And finally, we evaluate the performance of the proposed index and prove that the index processes history queries efficiently.

• Proceedings of the Korea Information Processing Society Conference
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• 2004.11a
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• pp.63-66
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• 2004

최근 시공간 데이터에 대한 관심이 늘어나면서 시간에 따라 이동하는 객체에 대한 처리와 이력 공간 정보를 처리하는 영역에 대한 연구가 활발하게 일어나고 있다. 이러한 시공간 데이터베이스에서의 효과적인 질의 처리를 위해 선택도 추정 기술의 요구가 생겨났다. 본 논문에서는 이력 공간 정보에 대한 선택도 추정을 위하여 T-Minskew 히스토그램을 구축하고 이를 이용하여 선택도 추정 방법을 제시한다. 또한 임계치 기법을 이용한 효과적인 히스토그램 유지 기법을 제시한다.

• Journal of KIISE:Databases
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• v.36 no.3
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• pp.198-214
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• 2009

Trajectories of RFID tags can be modeled as a line, denoted by tag interval, captured by an RFID reader and indexed in a three-dimensional domain, with the axes being the tag identifier (TID), the location identifier (LID), and the time (TIME). Distribution of tag intervals in the domain space is an important factor for efficient processing of a query for tracing tags and is changed according to arranging coordinates of each domain. Particularly, the arrangement of LIDs in the domain has an effect on the performance of queries retrieving the traces of tags as times goes by because it provides the location information of tags. Therefore, it is necessary to determine the optimal ordering of LIDs in order to perform queries efficiently for retrieving tag intervals from the index. To do this, we propose LID proximity for reordering previously assigned LIDs to new LIDs and define the LID proximity function for storing tag intervals accessed together closely in index nodes when a query is processed. To determine the sequence of LIDs in the domain, we also propose a reordering scheme of LIDs based on LID proximity. Our experiments show that the proposed reordering scheme considerably improves the performance of Queries for tracing tag locations comparing with the previous method of assigning LIDs.

• Journal of KIISE:Databases
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• v.33 no.6
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• pp.578-589
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• 2006

Owing to the proliferation of Radio Frequency Identification (RFID) technologies which is being watched as a core technology of ubiquitous computing, applications which offer convenience to people using RFID technologies are more and more increased. To easily develop these applications, a middleware system which acts as a bridge between RFID hardware and application is essential. In this paper, we propose a novel XML-based RFID middleware system called UbiCore (Ubiquitous Core). UbiCore has following features: First, UbiCore employs its own query language called XQueryStream (XQuery for Stream Data) which is originated from XQuery. Second, UbiCore has the preprocessing phase called pre-filtering prior to query evaluation and reuses the intermediate result of previous evaluation to speed up the processing of RFID tag data stream. Third, UbiCore supports query on both continuously generated stream data and archived historical data. And last, UbiCore offers a distinct markup language called Context-driven Service Markup Language (CSML) to easily specify the linking information between context and service.