• Journal of KIISE:Databases
• /
• v.27 no.1
• /
• pp.53-63
• /
• 2000

The mobile computing service market is increasing rapidly due to the development of low-cost wireless network technology and the high-performance mobile computing devices. In recent years, several methods have been proposed to effectively deal with restrictions of the mobile computing environment such as limited bandwidth, frequent disconnection and short-lived batteries. Amongst those methods, much study is being done on the caching method - among the data transmitted from a mobile support station, it selects those that are likely to be accessed in the near future and stores them in the local cache of a mobile host. Existing cache replacement methods have some limitations in efficiency because they do not take into consideration the characteristics of user mobility and spatial attributes of geographical data. In this paper, we show that the value and the semantic of the data, which are stored in the cache of a mobile host, changes according to the movement of the mobile host. We argue it is because data that are geographically near are better suited to provide an answer to a users query in the mobile environment. Also, we define spatial location of geographical data has effect on, using the spatial attributes of data. Finally, we propose two new cache replacement methods that efficiently support user mobility and spatial attributes of data. One is based on the location of data and the other on the meaningful region of data. From the comparative analysis of the previous methods and that they improve the cache hit ratio. Also we show that performance varies according to data density using this, we argue different cache replacement methods are required for regions with varying density of data.

• Journal of Korea Spatial Information System Society
• /
• v.2 no.2 s.4
• /
• pp.99-115
• /
• 2000

A geographic information system (GIS) generally has a great deal of geographic data and has a singular storage structure individually. It is very hard to exchange geographic data between geographic information systems which store their geographic data with incompatible formats. Moreover, since it needs large amount of storage space to store geographic data and expensive cost to input them. In this paper, we designed and implemented a SDTS (Spatial Data Transfer Standard) Data Conversion System for Gothic which is an existing geographic information system. In order to convert geographic data without loss of information, we first carefully define a mapping between SDTS data and Gothic data. Especially, since SDTS data are in the format of ISO8211, the FIPS123 library is used to access them. Because the internal data format of Gothic is not open to the public, we also use the Gothic library to access Gothic data. The SDTS data conversion system developed in this paper uses an intermediate file to convert geographic data efficiently. In addition, we use UIL (User Interface Language) to implement a graphic user interface (GUI) of our system.

• Journal of Korea Spatial Information System Society
• /
• v.1 no.2 s.2
• /
• pp.33-46
• /
• 1999

In distributed computing platforms like CORBA, wrappers are used to integrate heterogeneous systems or databases. A spatial data provider is one of the wrappers because it provides clients with uniform access interfaces to diverse data sources. The individual implementation of spatial data providers for each of different data sources is not efficient because of redundant coding of the wrapper modules. This paper presents a new architecture of the spatial data provider which consists of two layered objects : independent wrapper components and dependent wrapper components. Independent wrapper components would be reused for implementing a new data provider for a new data source, which dependent wrapper components should be newly coded for every data source. This paper furthermore discussed the issues of implementing the representation of query results in the middleware. There are two methods of keeping query results in the middleware. One is to keep query results as non-CORBA objects and the other is to transform query results into CORBA objects. The evaluation of the above two methods shows that the cost of making CORBA objects is very expensive.

• Journal of KIISE:Databases
• /
• v.31 no.2
• /
• pp.163-173
• /
• 2004

Recently, location-based services are becoming very Popular in mobile environments. In this paper, we propose a new association based prefetch algorithm (called by STAP) that efficiently supports information service based on the large quantity of spatial database in mobile environments. We apply the spatial-temporal relations that are meaningful for location-based queries in mobile environments. Moreover, STAP considers user's mobility and the weight of spatial data. The relation of services is a new aspect not considered in previous cache politics. So STAP is the first prefetch algorithm considering the spatial-temporal relations and thus the cache policy begins to gain a new dimension. We evaluate the performance of STAP and prove the efficiency of STAP.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.1 no.2
• /
• pp.67-79
• /
• 1998

Most GIS applications are read-intensive on a large number of spatial objects and when the spatial objects are composite objects, the contained objects within the composite objects are also accessed. In GIS applications, creation, deletion, and update operations on spatial objects occur very rarely, but once they occur they deal with a large number of spatial objects. This paper proposes the concept of the multi-level pre-fetch query to retrieve a large number of spatial objects efficiently, and the functionality of the deferred-flush on the newly created persistent objects into the database with the optimal performance, and presents the design and implementation details of those ideas into an object-oriented DBMS BADA-III while considering these characteristics of GIS applications. The multi-level pre-fetch query retrieves the objects that satisfy the query and the objects that are contained within the objects up to the level specified by users, and registers the retrieved objects on the client cache. The deferred-flush flushes a large number of composite objects that are created by the application with a minimal overhead of the server and a minimal number of communications between the client and the server. These two functionality are suitable for the applications that search or create a large number of composite objects like GIS applications.

• Journal of KIISE:Databases
• /
• v.30 no.3
• /
• pp.273-285
• /
• 2003

Generally, vector spatial data, with richer information than raster spatial data enabledata, enables a mere flexible and effective manipulation of the data sets. However, one of challenges against the publication of vector spatial information on the Internet is the efficient transmission of the big and complex vector spatial datadata, which is both large and complex, across the narrow-bandwidth of the Internet. This paper proposes a new transmission method, namely, the Scale-Dependent Transmission method, with the purpose of improving the efficiency of vector spatial data transmission on the narrow-bandwidthacross the Internet. Simply put, its nam idea is “Transmit what can be seen””. Scale is regarded as a factor naturally associated with spatial features so that not all features are visible to users at a certain scale. With the aid of the Wavelet-Wavelet-based Map Generalization Algorithm, the proposed method filters out invisible features from spatial objects according to the display scale and then to transmit onlytransmits only the visible features as athe final answer for an individual operation. Experiments show that the response times ofan individual operation has been reducedoperations were substantially by the usage of reduced when using the proposed method.

• Journal of KIISE:Software and Applications
• /
• v.26 no.10
• /
• pp.1156-1166
• /
• 1999

의사결정 시스템은 전사적인 의사결정과 전략적 정보수집을 위해 거대한 량의 정보를 빠른 시간내에 제공할 것을 요구한다. 데이타 웨어하우스는 이러한 정보를 신속히 제공하기 위해 여러 지역 데이타베이스로부터 필요한 정보를 사전에 추출하고 가공 및 통합하여 별도의 저장공간에 저장한다. 일반적으로, 웨어하우스 내의 정보는 지역 데이타베이스에 저장된 정보에 대한 실체화된 뷰로서 간주하며 지역 데이타의 변경에 따라 일관성을 유지하도록 반영해야 한다. 본 논문에서는 일관성을 유지하기 위해 정보 공유가 가능한 데이타 웨어하우스 시스템의 구조와 비-보상 실체 뷰 관리 기법을 제안한다. 본 논문에서 제안한 데이타 웨어하우스 시스템의 구조는 지역 데이타베이스에서 추출된 정보를 관리하는 별도의 지역 정보 관리자를 두어 뷰 관리자들 간의 정보 공유가 가능하게 한다. 비-보상 실체 뷰 관리 기법은 지역 데이타 변경 사건에 따른 뷰 관리 시 다른 사건에 의해 영향을 받지 않도록 하기 때문에 기본의 사전 보상이나 나중 보상 기법과는 달리 추가적인 질의 처리를 요구하지 않는 기법이다.Abstract A decision support system(DSS) commonly requires fast access to tremendous volume of information. A data warehouse is a database storing the information that is extracted, filtered and integrated from several relevant local databases to reply upon aggregated queries. The information stored in the data warehouse can be regarded as materialized views. The materialized view has to be modified according to the change of the corresponding local databases to preserve the data consistency. In this paper, we propose a data warehousing system architecture allowing information sharing (DAWINS), and a non-compensating materialized view maintenance algorithm(NCA). DAWINS architecture allows relevant information to be shared by individual view managers with local data manager for each local database. Unlikely to the pre- or post-compensating algorithms, which are required to remove the effects of some events to other view in the process of view maintenance, NCA does not require any additional query processing, since a local data manager in DAWINS already maintains the effects of update events occurring in local systems.

• Journal of Korean Society for Geospatial Information Science
• /
• v.4 no.1 s.6
• /
• pp.23-29
• /
• 1996

The purpose of this study is to develope an Object-Oriented Graphic database management system to handle geographic data of geographic information systems. As the result of this study, unstructured vector model was developed to handle geographic data and graphic database management was implemented by object-oriented programming. This study was focused on liking function between graphic data and attribute data, and not focused on network analysis function.

• Proceedings of the Korean Information Science Society Conference
• /
• 2001.10a
• /
• pp.85-87
• /
• 2001

최근 지리 정보 시스템(GIS)이 전 국가적으로 대중화되면서 지리 정보가 다양한 분야와 다양한 서버 환경에서 사용되고 있다. 따라서, 이렇게 다양해진 지리 정보를 효율적으로 사용하기 위해선 지리 정보 시스템의 상호운용성은 필수적이다. 이를 지원하기 위해서 OGC(Open GIS Consortium)에서는 상호운용성에 대한 표준 명세인 OpenGIS(Open Geodata Interoperability Specification)를 제시하였으며, 또한 이를 웹 환경에서 검증하고 활용하기 위해 웹 매핑 테스트 베드에서 여러 가지 시도를 하고 있다 이러한 시도 중 하나로 웹 환경의 이질적인 지리 정보를 공통적으로 표현하기 위해 지리정보를 구조화된 문서인 XML(eXtensible markup Language)로 인코딩하는 GML(Geography Markup Language) 명세를 제시하였다. 본 논문에서는 다양한 환경에서 지리 정보를 표현하기 위한 GML 2.0 명세와 GML 2.0 에서 사용하고 있는 XML 스키마 명세를 분석하였다. 또한, 이를 토대로 사용자들이 GML 2.0 문서를 쉽게 생성, 디스플레이, 편집할 수 있도록 함은 물론 기존의 공간 데이타베이스 시스템의 지리 정보를 GML 2.0 문서로 변환하고, 반대로 GML 2.0 문서를 공간 데이타베이스로의 변환을 쉽게 할 수 있는 GML문서 관리 시스템을 설계 및 구현하였다.

• 한국공간정보시스템학회:학술대회논문집
• /
• 2003.11a
• /
• pp.91-97
• /
• 2003

지리공간 정보가 사용되는 분야나 환경에 따라 사용되는 표준 데이타 포맷이 다르므로 다른 환경의 지리공간 정보를 활용하기 위해서는 자신의 환경에 맞는 데이타 포맷으로 변환하는 작업이 필요하게 되었다 또한, 다양한 분야의 지리공간 정보를 상호 운용이 가능하도록 지리공간 정보를 엔코딩해 주는 지리공간 정보 엔코딩 서비스 시스템이 요구되게 되었다. 이에 본 논문에서는 지리공간 정보를 OGC의 GML 3.0으로 엔코딩해 주는 GML 기반 지리공간 정보 엔코딩 서비스 시스템을 설계 및 구현하였다. 특히, 지리공간 정보를 간편하고 효율적으로 엔코딩하기 위해 엔코딩 방법을 정의하는 매핑 규칙을 활용하였다. 본 논문에서 구현한 GML 기반 지리공간 정보 엔코딩 서비스 시스템을 활용해 공간 데이타베이스 시스템인 ZEUS에 구축된 지리공간 정보를 GML 3.0으로 엔코딩 하거나, 역으로 GML 3.0을 ZEUS의 지리공간 정보로 엔코딩하여 상호 운용할 수 있다.