• The KIPS Transactions:PartD
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• v.11D no.2
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• pp.317-324
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• 2004

Containment queries for XML documents is one of the most important query types, and thus the efficient support for this type of query is crucial for XML databases. Recently, object-relational database management system (ORDBMS) vendors try to store and retrieve XML data in their products. In this paper, we propose an extensible index to support containment queries over the XML data stored as BLOB type in ORDBMSs. That is, we describe how to implement the index using the extensibility feature of an ORDBMS, and describe its usage.

• Proceedings of the Korea Information Processing Society Conference
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• 2002.04a
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• pp.63-66
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• 2002

XML 저장소 내에 XML 문서들과 그들로부터 도출된 XML 실체뷰가 있다고 가정할 때, XML 문서 검색의 성능 향상을 위해서 이들 실체뷰를 이용하여 질의를 처리할 수 있다. 즉, 하부 XML 문서에 대한 원래의 질의를 관련된 실체뷰에 대한 질의로 변환하여 수행함으로써 질의 응답시간을 줄일 수 있다. 실체뷰를 이용한 질의 처리의 유형으로는 (1) 실체뷰로부터 원하는 결과를 모두 얻을 수 있는 유형과 (2) 질의 결과의 일부는 실체뷰에 존재하지만 일부는 하부 XML 문서로부터 검색해야 하는 유형이 있다. 본 논문에서는 두번째 유형에 대하여 연구하였다. 주어진 질의를 (1) 실체뷰에 대한 질의와 하부 데이타에 대한 질의로 분할하여 처리한 후 두 결과를 통합하는 방법과 (2) 원래의 질의를 실체뷰를 이용하지 않고 처리하는 방법 간의 성능을 비교, 분석하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2003.05c
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• pp.1535-1538
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• 2003

웹 상의 데이터 교환 표준으로 XML이 등장한 이래 XML 데이터를 관계 DBMS에 저장하고 질의 처리를 수행하는 기법에 관한 연구가 활발히 수행되고 있다. 전통적인 데이터베이스에서처럼 단일 또는 복수개의 XML문서에 대한 XML 질의를 통해 XML 뷰를 정의할 수 있고 이는 질의 처리 성능 향상을 위해 웹 환경에서 실체화될 수 있다. 본 논문에서는 XML 데이터를 관계 DBMS에 저장하였을 때 XML 질의의 결과를 실체뷰로 캐쉬하였다가 동일 질의가 반복될 때 캐쉬를 이용한 응답을 수행하기 위한 XML 뷰 실체화 모델을 세 가지 제시하고 비교, 평가한다.

• Journal of KIISE:Databases
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• v.34 no.3
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• pp.270-281
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• 2007

Recently, there has been growing interest in streaming XML data. Much of the work on streaming XML data has been focused on efficient filtering of XML data. Such XML filtering systems deliver XML documents to interested users. The burden of extracting the XML fragments of interest from XML documents is placed on users. As a result, several evaluation techniques for streaming XML data, which only extract interested XML fragments by directly evaluating XML queries on streaming XML data, have been proposed. However, existing evaluation techniques for streaming XML data only support the restricted subset of XPath queries, and multiple queries cannot be evaluated by such evaluation techniques. In this paper, we propose XTREAM which evaluates multiple queries in conjunction with the read-once nature of streaming data. In contrast to the previous work, XTREAM supports a wide class of XPath queries including order based predicates and so on. Experimental results with real-life and synthetic XML data demonstrate the efficiency and scalability of XTREAM.

• Journal of KIISE:Databases
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• v.33 no.3
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• pp.327-341
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• 2006

As we are getting to deal with more applications that generate streaming data such as sensor network, monitoring, and SDI (selective dissemination of information), active research is being conducted to support efficient processing of queries over streaming data. The applications on the Web environment like SDI, among others, require query processing over streaming XML data, and its investigation is very important because XML has been established as the standard for data exchange on the Web. One of the major problems with the previous systems that support query processing over streaming XML data is that they cannot deal adaptively with dynamically changing stream because they rely on static query plans. On the other hand, the stream query processing systems based on relational data model have achieved adaptiveness in query processing due to query operator routing. In this paper, we propose a system of adaptive query processing over streaming XML data in which the model of adaptive query processing over streaming relational data is applied. We compare our system with YFiiter, one of the representative systems that provide XML stream query processing capability, to show efficiency of our system.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.45-49
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• 2000

다양한 정보 형태를 가진 전자 문서의 효과적인 관리를 위해 XML과 관련된 연구들이 활발히 진행되고 있다. 그러나 XML과 관련된 대부분의 연구들은 XML 문서들을 저장, 관리 및 검색할 수 있는 XML 저장 관리 시스템을 대상으로 하고 있다. 본 논문에서는, 실제 Web 상에 분산되어 저장된 전자 문서들 중 하이퍼링크로 연결된 XML 문서들을 대상으로 사용자 질의에 대해 효율적인 검색을 지원해주기 위해, XML 링크 정보를 추출하여 참조하는 검색 질의 처리 방안을 제시한다. 이를 위해 링크 정보를 저장하는 링크 정보 관리 테이블의 구조, 링크 정보를 활용한 XML 문서의 검색 모델, XML 문서의 검색 질의 처리 방안, 그리고 링크 정보의 갱신을 질의 처리 중에 부가적으로 수행하는 방안을 기술하였다. 주어진 사용자 질의에 대한 처리 과정 중 링크와 관련된 질의 처리에 대해 추출된 링크 정보를 이용하여 부질의를 생성하고 처리할 수 있도록 하였다.

• The KIPS Transactions:PartD
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• v.10D no.4
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• pp.621-638
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• 2003

As demand of XML documents in the Web increases, Web service applications that manage XML documents as their resource are increasing. The view mechanism for XML data could be considered for effective in query processing in these Web service applications. If the XML query results are maintained as XML materialized views and their relevant XML query is processed using them, the query response time could be reduced. There are two types of processing an in path expression, which is one of the core features of XML query languages, using XML materialized views. One is the type where the complete query result is obtained from the materialized view, and the other is the type where some of the result is obtained from the materialized view and the rest is from the underlying XML documents. In this paper, we investigate the second type. An XML query in this paper is an XML path expression which is one of the core features of XML query languages. We first describe the storage structures of the XML materialized views derived from the underlying XML documents in the XML repository. Then, we propose the algorithms to decompose a given XML query into the subquery against the materialized view and the subquery against the underlying XML documents, and to integrate the results of these subqueries. Through performance evaluation, we figure out the condition under which our XML query decomposition using materialized views is more effective than the conventional processing.

• 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.

• 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.

• The Journal of Society for e-Business Studies
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• v.14 no.4
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• pp.75-94
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• 2009

Since XML emerged as a standard for data exchange on the web, it has been established as a core component in e-Commerce and efficient query processing over XML data in ubiquitous computing environment has been also receiving much attention. Recently, the techniques were proposed whereby an XML document is fragmented into XML fragments to be streamed and the mobile clients receive the stream while processing queries over it. In processing queries over an XML fragment stream, the average access time significantly depends on the order of fragments in the stream. As such, for query performance, an efficient organization of XML fragment stream is required as well as the indexing for energy-efficient query processing due to the reduction of tuning time. In this paper, a technique of XML fragment stream organization based on query frequencies, fragment size, fragment access frequencies, and an active XML-based indexing scheme are proposed. Through implementation and performance experiments, our techniques were shown to be efficient compared with the conventional XML fragment stream organizations.