• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.7-9
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• 2002

XML 문서를 관계형 데이타베이스에 저장하는 것은 관계형 데이타베이스 관리 시스템이 제공하는 안정성과 질의 능력을 활용하고자 하는 것이 주된 요인이다. 관계형 데이타베이스는 2차원의 테이블 구조를 저장하고 응용하는 것에 특화되어 있으므로 XML 문서에 표현되어 있는 계층적 구조, 중첩 구조 등 이질적인 요소들을 관계형 데이타베이스에 반영하는 모델링 방법으로 현재가지 완벽하게 실용화된 것은 없다. 본 논문은 XML 문서를 관계형 데이타베이스에 저장하기 위한 스키마 구조를 제안하고 XML 문서를 바다 -II에 저장, 검색, 재구성만 구현 결과를 제시한다.

• Journal of KIISE:Databases
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• v.31 no.6
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• pp.684-698
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• 2004

The Hippocratic database model recently proposed by Agrawal et al. incorporates privacy protection capabilities into relational databases. Since the Hippocratic database is based on the relational database, it needs extensions to be adapted for XML databases. In this paper, we propose the Hippocratic XML database model, an extension of the Hippocratic database model for XML databases and present an efficient access control mechanism under this model. In contrast to relational data, XML data have tree-like hierarchies. Thus, in order to manage these hierarchies of XML data, we extend and formally define such concepts presented in the Hippocratic database model as privacy preferences, privacy policies, privacy authorizations, and usage purposes of data records. Next, we present a new mechanism, which we call the authorization index, that is used in the access control mechanism. This authorization index, which is Implemented using a multi-dimensional index, allows us to efficiently search authorizations implied by the authorization granted on the nearest ancestor using the nearest neighbor search technique. Using synthetic and real data, we have performed extensive experiments comparing query processing time with those of existing access control mechanisms. The results show that the proposed access control mechanism improves the wall clock time by up to 13.6 times over the top-down access control strategy and by up to 20.3 times over the bottom-up access control strategy The major contributions of our paper are 1) extending the Hippocratic database model into the Hippocratic XML database model and 2) proposing an efficient across control mechanism that uses the authorization index and nearest neighbor search technique under this model.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.109-111
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• 2003

관계형 데이타베이스에 저장되어 있는 데이타를 XML 문서로 추출하기 위해서는 데이블에 저장된 데이타를 XML 문서 형식에 맞는 계층적인 관계를 가지도록 구조화하는 과정이 필요하다. 본 논문에서는 관계형 데이타베이스를 사용하는 XML 저장 및 검색 시스템인 eXDM(embedded XML Database Management System)의 내부에서 구현한 XML 문서 추출 서브시스템에 대하여 기술한다. 이 시스템은 XML 문서에 대한 질의(XQuery)의 RETURN 절과 SORTBY 절을 분석하여, 관계형 데이타베이스에 저장되어 있는 데이타를 구조화하여 계층적인 구조를 가지는 XML 문서 형태로 추출한다.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.5
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• pp.383-391
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• 2001

The value of XML as electronic documents is increasing nowadays. The XML document has properties of semistructured data. It can be modeled as object-oriented model which can be easily adapted by object-oriented database. For storing XML documents to conventional database system, extracting schema information from the DTD of a XML document has been studied for several years. In this paper we store XML documents into object-oriented database, which preserve the semantics of the documents. We can store and query by OQL and make applications by C++ and make applications by C++ binding which is the access method of object-oriented database. Therefore, existing database applications can be used without modification.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.31-33
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• 2003

문서를 표현하는 여러 가지 기법 중에서 XML(eXtensible Markup Language)은 확장성과 범용성 때문에 데이타의 교환과 표현에 대한 표준으로 자리잡고 있다. 이에 XML로 데이타를 저장하기 위한 다양한 방법들이 제시되고 있다. 본 논문에서는 관계형 데이타베이스에 XML 데이타를 저장하기 위해 XML 데이터의 타입을 관계형 데이타베이스의 타입으로 매칭해 주는 서브시스템인 타입 처리기를 구현한다. 타입 처리기에서는 eXDM이 내장형 시스템이라는 제한사항을 고려하고, XQuery 형태의 질의문을 지원하기 위해 XML-스키마를 변형한 형태의 XML 타입 정의 문서를 이용한다.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.540-551
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• 2003

Recently, several works have been proposed for updating XML documents［l-3] stored in databases. These researches defined update operations and resolved some semantic problems. Because the update operations are usually validated after execution, several conflicts nay occur. For solving these conflicts, XML database systems must be able to validate an update operation immediately according to DTD before the update operation is executed. Furthermore, in many studies for updating, they just validate whole XML documents and can't validate parts of them. If updates are very frequent, validating whole XML documents will cause performance degradation. In this paper, we propose solutions for these two problems. We extract and store DTD information. Then, when an XML document stored in the database is updated, we verifies whether the update is valid or not by using the information. Consequently, XML database systems can always maintain valid XML documents. The validity of update operations is checked immediately before the actual update operation is applied to the database and the validation is performed on only updated parts of an XML document in the database.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.22-24
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• 2002

XML이 웹상에서 데이타 교환의 표준으로 채택되면서 XML 데이타를 관계형 데이타베이스를 이용하여 저장하고 처리하는 것이 많이 연구되고 있다. 본 연구에서는 관계형 데이타베이스에 저장되어 있는 XML 데이타의 효과적인 질의 처리에 사용할 수 있는 인덱스 구조로서 디렉토리 인덱스를 제안한다. 디렉토리 인덱스는 정규 경로식 처리에 있어서 비트맵을 이용하여 조인 연산을 크게 줄여 처리 시간이 빠르며 인덱스의 갱신에도 효과적으로 대처할 수 있다.

• Journal of KIISE:Databases
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• v.32 no.5
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• pp.473-486
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• 2005

The Hippocratic database model recently proposed by Agrawal et at. incorporates privacy protection capabilities into relational databases. The authors have subsequenty proposed the Hippocratic XML daかabase model[4], an extension of the Hippocratic database model for XML databases. In this paper, we propose a new concept that we cail the dynamic predicate(DP) for effective access control in the Hippocratic XML database model. A DP is a novel concept that represents a dynamically constructed rendition that tan be adapted for determining the accessibility of elements during query execution. DPs allow us to effectively integrate authorization checking into the query plan so that unauthorized elements are excluded in the process of query execution. Using synthetic and real data, we have performed extensive experiments comparing query processing time with those of existing access control mechanisms. The results show that the proposed access control mechanism improves the wall clock time by up to 219 times over the top-down access control strategy and by up to 499 times over the bottom-up access control strategy. The major contribution of our, paper is enabling effective integration of access control mechanisms with the query plan using the DP under the Hippocratic XML database model.

• Journal of KIISE:Computing Practices and Letters
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• v.7 no.3
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• pp.202-210
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• 2001

Recently, XML is emerging as a web document standard and researches on storing and querying XML documents using existing RDBMS are actively in progress. In this paper, we propose a method that enables users to view and use XML documents like a relational table by extending concept of RDBMS's SQL view and. table function. In our approach, XML documents are existed independently of RDBMS and users can register relational schema of necessary part of XML document by using XML-View definition statement. Registered XML-View can be queried by SQL, and XML -table function is internally used so that XML - View can be accessed and used like a relational table. The proposed method enables users to access XML documents by providing the XML- View definition syntax and the table-function for existing RDBMS. Also, when schema modification for XML is needed, user can handle by modification of the XML- View definition.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.195-204
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• 2004

The Semantic Web is proposed as the next generation Web technology. In the environment of the Semantic Web, resources are related with each other semantically and computers can process this information easily. The Resource Description Framework (RDF) supports this semantic relationship. RDF is the data model for describing metadata of the Web resources. To establish and develop the Semantic Web, methods for managing RDF data efficiently are the most important. So, in this research, we propose methods for storing and querying RDF data using an XML database system. Using an XML database system, XML data, main data of the Semantic Web, and RDF data, the metadata of XML data, can be managed in the same storage and by the same mechanism efficiently. In addition, we propose an efficient data retrieval method and several techniques to improve the system performance. Our query processing technique performs better than an existing system.