• Journal of Korea Multimedia Society
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• v.10 no.3
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• pp.289-302
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• 2007

The existing query processing technique for CXQuery, which is able to query regardless of knowledge about XML document structures, is difficult to manage because of table join for query processing and results return, mapping XML documents into relational tables, and so on. In this paper we have developed a converter capable of converting CXQuery to XQuery in order to make use of the query processing techniques for XQuery progressing standardization. The converting speed of the converter takes a trifling time as much as negligible quantities in comparison with the total query processing time. This is also able to query directly XML documents regardless of relational databases, and users can query without knowledge about XML document structures.

• Journal of KIISE:Databases
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• v.32 no.2
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• pp.204-218
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• 2005

XML has rapidly emerged as the standard for the interchange of data in numerous application areas. To support for efficient queries against XML data, many query languages have been designed. The query languages require the users to know the structure of the XML documents and specify search conditions on the structure. This path-based query against XML documents is a natural consequence of the hierarchical structure of XML. However, it is also desirable to allow the users to formulate no path queries against XML documents, to complement the current path-based queries. In this paper, we design a query expression capable of querying without knowledge about the structure of XML documents, and develop a query processor to evaluate no path queries.

• The KIPS Transactions:PartD
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• v.17D no.5
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• pp.353-358
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• 2010

Unlike the traditional databases, queries on XML streams are restricted to a real time processing and memory usage. In this paper, a robust labeling scheme is proposed, which quickly identifies structural relationship between XML fragments. The proposed labeling scheme provides an effective query processing by removing many redundant operations and minimizing the number of fragments being processed. In experimental results, the proposed labeling scheme efficiently processes query processing and optimizes memory usage.

• 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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• 2002.10c
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• pp.100-102
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• 2002

XML 문서에 대한 다양한 질의를 위해서 W3C에서는 XQL, XML-QL, XML-GL, XQUERY와 같은 질의어를 제안하였다. 이들 질의어는 다양한 질의 유형의 분류와 표현은 가능하나, 조인 질의의 경우 단순 조인 질의만을 지원할 뿐, XML 문서의 구조나 텍스트 정보의 유사성을 이용한 보다 다양한 조인 질의에 대한 연구가 미비하였다. 본 논문에서는 다중 문서에 대한 조인 질의를 체계적이고 효과적으로 표현하기 위해, 문서에 대한 조인 질의를 여러 타입으로 분류하였다. 또한 효율적인 질의처리를 위하여 다양한 일반 조인 질의 및 정보검색 기능을 지원하는 유사성 조인 연산자(similarity join operator), 순수 구조 기반 조인을 지원하는 구조 조인 연산자(structured join operator)를 지원하도록 XML 질의어인 QUILT를 확장하였다. 특히, 구조 정보만을 이용한 질의시 구조의 깊이(depth)정보를 이용하여 사용자의 요구에 맞게 질의 검색 범위를 설정하고, XML 문서에 대한 질의 문을 좀더 간결하게 표현할 수 있도록 설계하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2002.10c
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• pp.85-87
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• 2002

XML을 관계형 데이터베이스 기술과 접목시키는 하나의 방법으로 관계형 데이터베이스의 내용을 표현하는 가상의 XML 뷰를 제공하고 그 부에 대하여 XQuery의 질의를 요구하는 환경을 고려할 필요가 있다. 본 논문은 가상의 XML 뷰와 관계형 데이터베이스 사이의 매핑, 그 뷰를 기반으로 하는 XQuery 질의를 관계형 데이터베이스에서 처리할 수 있는 SQL 질의로 변환, 관계형 데이터베이스 시스템이 SQL 질의를 처리한 결과를 XML 문서로 변환하는 기법을 제시한다.

• The KIPS Transactions:PartD
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• v.11D no.7 s.96
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• pp.1375-1384
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• 2004

Streaming data processing is an area of interest with much research under way. There has been increasing attention on the demands for efficient processing of streaming data produced in the application areas such as monitoring and sensor network. We have developed a continuous query processing system for streaming data and evaluated its performance in this paper. XML, the standard for data exchange on the web, is used as the model for the streaming data and the XQuery appended with a time interval is adopted as the query language for expressing con-tinuous queries. In the proposed system, the result is produced through background processing and materialized for reute in subsequent query processing. Through a detailed set of performance experiments, we shoed the effectiveness of the proposed system.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.65-68
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• 2010

스트리밍 XML 데이터는 고정된 저장소에 유지되지 않고 사용자 측으로 계속적으로 데이터가 전송된다는 특성을 지닌다. 이러한 스트리밍 XML에 대한 질의 처리를 위해서는 효과적인 메모리 관리와 빠른 질의 처리 성능이 요구된다. 최근 최소한의 메모리 사용으로 효과적으로 트윅 질의를 처리하기 위한 기법인 StreamTX가 제안되었으나 반복적인 질의 처리 알고리즘 호출로 인해 불필요한 질의 처리시간이 발생한다. 따라서, 본 논문에서는 이러한 불필요한 질의 처리 시간을 줄이기 위해 실시간으로 질의와 무관한 노드를 제거하여 보다 효과적인 질의 처리를 수행 기법을 제안한다. 제안된 기법은 기존 연구와 유사한 메모리 사용량을 가지면서도 빠른 질의 처리 속도를 가짐을 성능평가를 통해 검증한다.

• Journal of KIISE:Databases
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• v.37 no.3
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• pp.146-164
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• 2010

Due to an increasing volume of XML data, it is considered prudent to store XML data on an industry-strength database system instead of relying on a domain specific application or a file system. For shredded XML data stored in relational tables, however, it may not be straightforward to apply existing algorithms for twig query processing, since most of the algorithms require XML data to be accessed in a form of streams of elements grouped by their tags and sorted in a particular order. In order to support XML query processing within the common framework of relational database systems, we first propose several bitmap indexes and their strategies for supporting holistic twig joining on XML data stored in relational tables. Since bitmap indexes are well supported in most of the commercial and open-source database systems, the proposed bitmapped indexes and twig query processing strategies can be incorporated into relational query processing framework with more ease. The proposed query processing strategies are efficient in terms of both time and space, because the compressed bitmap indexes stay compressed during data access. In addition, we propose a hybrid index which computes twig query solutions with only bit-vectors, without accessing labeled XML elements stored in the relational tables.

• The KIPS Transactions:PartD
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• v.13D no.1 s.104
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• pp.11-22
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• 2006

As we are to deal with more and more XML documents, research on storing and managing XML documents in databases are actively conducted. Employing RDBMS or ORDBMS as a repository of XML documents is currently regarded as most practical. The query results out of XML documents stored in databases could be cached for query performance though the cost of cache consistency against the update of the underlying data is incurred. In this paper, we assume that an ORDBMS is used as a repository for the XML query cache as well as its underlying XML documents, and that XML query cache is refreshed in a deferred way with the update log. When the same XML document was updated multiple times, the deferred refresh of the XML query cache may Bet inefficient. We propose an algorithm that removes or filters such duplicate updates. Based on that, the optimal SQL statements that are to be executed for XML query cache consistency are generated. Through experiments, we show the efficiency of our proposed deferred refresh of XML query cache.