• Proceedings of the Korea Information Processing Society Conference
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• 2001.04a
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• pp.23-26
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• 2001

XQL은 W3C에 의해 제안된 XML 질의 언어 중 하나다. XML 문서 검색의 성능 향상을 위해서 XML 저장소에는 XML 문서들 외에 그들로부터 도출된 XML 뷰를 실체 뷰로 저장해 둘 수 있는데, 이들 실체 뷰는 XQL과 같은 XML 질의어로 명시된 질의 처리에 이용될 수 있다. 즉, XML 저장소에 대한 XQL 질의가 주어졌을 때 그 결과를 XML 실체 뷰로부터도 얻을 수 있다면 원래의 질의를 실체 뷰에 대한 질의로 변환하여 수행함으로써 XQL 질의 처리의 성능 향상을 가져올 수 있다. 본 논문에서는 XML 저장소 내에 XML 실체 뷰가 있다고 가정하고 이를 이용한 XQL 질의 처리의 성능을 XML 실체 뷰를 이용하지 않는 경우와 비교, 평가한다.

• The KIPS Transactions:PartD
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• v.8D no.5
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• pp.461-472
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• 2001

Recently, much research on XML query processing considering the structural characteristics of XML documents is conducted, focusing primarily on the development and/or extension of XML query languages and on query optimization for effective retrieval of XML documents. In the XML repository, the XML views derived from the underlying XML documents could be stored materialized for effective retrieval of XML documents, and could be capitalized on for XML query processing In this paper, assuming that the XML views defined in XQL are materialized in the repository, we investigate XQL query processing that capitalizes on them. We describe the storage structure of the XML repository which supports the materialized views, and propose an algorithm that determines whether the given XQL query can be processed with the relevant materialized view adn accordingly transforms the original query into one against it.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.243-253
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• 2005

Dissemination of XML data on the internet could breach the privacy of data providers unless access to the disseminated XML data is carefully controlled. Recently, the methods using encryption have been proposed for such access control. However, in these methods, the performance of processing queries has not been addressed. A query processor cannot identify the contents of encrypted XML data unless the data are decrypted. This limitation incurs overhead of decrypting the parts of the XML data that would not contribute to the query result. In this paper, we propose the notion of query-aware decryption for efficient processing of queries against encrypted XML data. Query-aware decryption allows us to decrypt only those parts that would contribute to the query result. For this purpose, we disseminate an encrypted XML index along with the encrypted XML data. This index, when decrypted, informs us where the query results are located in the encrypted XML data, thus preventing unnecessary decryption for other parts of the data. Since the size of this index is much smaller than that of the encrypted XML data, the cost of decrypting this index is negligible compared with that for unnecessary decryption of the data itself. The experimental results show that our method improves the performance of query processing by up to 6 times compared with those of existing methods. Finally, we formally prove that dissemination of the encrypted XML index does not compromise security.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.28-30
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• 2004

웹에서 XML 데이터의 양이 많아짐에 따라 XML 질의 처리를 신속하게 해주는 기술이 필요하게 되었다. 이를 가능하게 해주는 것이 XML 질의 캐슁이다. 자주 제기되는 질의에 대하여 질의 결과를 캐쉬한 후 동일 질의에 재사용 함으로써 빠른 응답속도를 보장할 수 있다. 본 논문은 XML질의 캐슁 기법 중 캐쉬되는 데이터의 공간 부담을 줄일 수 있는 XML 뷰 인덱싱 기법에 관한 것으로, 뷰 인덱스의 생성 및 실체화 기법을 제안하고 구현 및 실험을 통한 성능 평가 결과를 기술한다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04b
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• pp.16-18
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• 2002

XML 기반의 데이터베이스 통할을 위한 랩퍼 시스템은 자료 저장소의 내용을 XML로 표현한다. 본 논문은 관계형 데이터베이스의 내용을 XML 스키마로 표현하는 랩퍼 시스템에서 사용자가 XML 뷰를 정의했을 때, XML 뷰에 대한 사용자 질의어 처리에 대하여 논한다. XML 뷰를 정의하는 언어와 사용자 질의어가 모두 XQuery일 매, XML 뷰와 사용자 질의어의 합성, XQuery로 표현된 사용자 질의어를 SQL로 번역, 그리고 질의 결과를 XML 문서로 변환하는 XML 질의어 처리 알고리즘을 제 시 한다.

• Journal of KIISE:Databases
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• v.33 no.5
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• pp.551-562
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• 2006

XML query caching for XML database-backed Web applications began to be investigated recently. Despite its practical significance, efficiency of the storage schemes for cached query results has not been addressed. In this paper, we deal with the storage schemes for XML query cache. A fundamental problem that needs to be considered in designing an efficient storage structure for XML query cache is that there exist performance tradeoffs between the two major types of operations on a cached query result. The two are (1) retrieving the whole of it to return the query result and (2) updating just a small portion of it for its incremental refresh against the updates done to its source. We propose eight different storage schemes for XML query cache, which are categorized into three groups: (1) the schemes based on the plain text file, (2) the schemes based on the persistent DOM (PDOM) file, and (3) a scheme employing an RDBMS. We implemented all of them, and compared their performance with each other. We also compared our proposal with a storage scheme based on a current state-of-the-art XML storage scheme, showing that ours is more efficient.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.6-8
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• 2000

XML 문서의 폭발적인 확산에 따라 Web상의 각 사이트는 XML 문서를 분산 저장하여 관리하고 있다. 그리고 XML 문서들 간에는 다양한 링크를 통해 관련된 정보를 참조할 수 있다. 그러나 현재까지 XML과 관련하여, 링크를 지원하는 질의어 개발이나 링크를 활용한 XML 검색 시스템 개발에 대한 연구는 미비하다. 본 논문에서는, 실제 Web상에 분산되어 저장된 전자 문서들 중 하이퍼링크로 연결된 XML 문서들을 대상으로, 링크를 지원하기 위해 기존 XML 질의어를 확장에 대해 연구하였다. 이를 위해 XML 링크를 지원하는 질의의 유형을 분류하고, 링크를 지원하기 위한 XML 질의어의 확장에 대해 기술한다. 그리고 링크를 활용한 XML 질의 처리 방안에 대해 기술한다.

• The KIPS Transactions:PartD
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• v.8D no.4
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• pp.313-326
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• 2001

The XML that was proposed as a next-generation standard for describing Web documents is widely used in various Web-based applications. In addition, XML documents on the Web link each other by hyperlinks. The current works on XML focus on the XML storage system that can efficiently store, manage, and retrieve XML documents. However, the research on the query language that supports the XML links and on the XML retrieval systems to process the XML links, is little conducted until now. In this paper, we propose an extension of an XML query language for expressing the XML link query and its processing scheme. A link query is to retrieve contents from an XML document (a query document) and from the XML documents (referenced documents) that are referred to by the links in the query document. As far as retrieving from the referenced documents is concerned, the current practice is to manually generate queries to get the partial results, and to repeat such a procedure. The purpose of link query processing in this paper is to eliminate the manual work altogether in getting the complete query result. The performance analysis shows that our link query processing strategy outperforms the conventional approach including the manual tasks. The more links to the referenced documents and the more referenced documents there are in the site storing the query document, the more query processing time decreases.

• Journal of KIISE:Databases
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• v.30 no.6
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• pp.641-650
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• 2003

The eXtensible Markup Language(XML) is emerging as a standard format of data representation and exchange on the Internet. There have been researches about storing and retrieving XML documents using the relational database which has techniques in full growth about large data processing, recovery, concurrency control and so on. Since in previous systems same structure information and fundamental operation are used for processing of various kinds of XML queries, only some specific query can be efficiently processed not all types of query. In this paper, we propose a flexible query processing system. To process query efficiently, the proposed system analyzes regular path expression queries, and uses $\theta$-join operation using region numbering values to check ancestor-descendent relationship and equi-join operation using parent's region start value to check parent-child relationship. Thus, the proposed system processes efficiently XML regular path expressions. From the experimental results, we show that proposed XML query processing system is more efficient than previous systems.

• The KIPS Transactions:PartD
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• v.16D no.1
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• pp.27-42
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• 2009

In realizing ubiquitous computing, techniques of efficiently using the limited resource at client such as mobile devices are required. With a mobile device with limited amount of memory, the techniques of XML stream query processing should be employed to process queries over a large volume of XML data. Recently, several techniques were proposed which fragment XML documents into XML fragments and stream them for query processing at client. During query processing, there could be great difference in resource usage (query processing time and memory usage) depending on how the source XML documents are fragmented. As such, an efficient fragmentation technique is needed. In this paper, we propose an XML fragmentation technique whereby resource efficiency in query processing at client could be enhanced. For this, we first present a cost model of query processing over XML fragment stream. Then, we propose an algorithm for resource-efficient XML fragmentation. Through implementation and experiments, we showed that our fragmentation technique outperformed previous techniques both in processing time and memory usage. The contribution of this paper is to have made the techniques of query processing over XML fragment stream more feasible for practical use.