• Proceedings of the Korean Information Science Society Conference
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• 2002.10d
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• pp.637-639
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• 2002

XML 문서를 효과적으로 관리하고 검색하기 위한 다양한 XML 질의 언어에 대한 연구가 활발히 수행되고 있지만 다양한 XML 질의 언어의 구문은 일반 사용자들이 숙지하는데 어려움이 있고, 또한 텍스트 형태의 XML 문서는 계층적인 구조로 되어있어 이러한 XML 문서의 구조를 알아야만 질의를 할 수 있다는 문제점이 있다. 따라서 본 논문에서는 복잡한 XML 질의어 구문과 질의 대상인 XML 문서의 구조를 동시에 시각화하고, 사용자와의 상호작용을 통해 질의문을 자동으로 생성하고자 한다. 이를 위해 본 논문에서는 다음과 같이 세 가지 컴포넌트를 기반으로 자동 질의어 생성을 위한 visual query interface를 제안하였다. 이 컴포넌트는 계층적 XML 문서 구조를 보여주는 XML structure viewer, 질의에 사용되는 연산자들을 아이콘화한 operator panel, 그리고 이 두 컴포넌트의 상호작용으로 작성된 질의 구문을 문법적으로 검사하기 위한 query statements panel로 구성된다. 이를 통해 다양한 계층적인 XML 문서의 구조와 복잡한 XML 질의 언어의 구문에 대해서 잘 모르는 초보자라 하더라도 쉽게 XML 문서 상에서 질의를 할 수 있다.

• Journal of Digital Contents Society
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• v.8 no.4
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• pp.541-546
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• 2007

Traditional query processing method is not efficient for continuous queries with large continuous stream data. This paper proposes a data-driven query processing method for stream data. The structure of query plan and query execution method are presented. With the proposed method, multiple query processing and sharing among queries can be achieved. Also query execution time can be reduced by storing partial results of query execution. This paper showed an example of query processing with XML data and XQuery query.

• Journal of the Korea Society of Computer and Information
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• v.11 no.5 s.43
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• pp.127-137
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• 2006

We propose two phase filtering scheme to develop an efficient mechanism for XML databases to control query-based access. An access control environment for XML documents and some techniques to deal with fine-grained authorization priorities and conflict resolution issues are proposed. Despite this, relatively little work has been done to enforce access controls particularly for XML databases in the case of query-based access. The basic idea utilized is that a user query interaction with only necessary access control rules is modified to an alternative form through a query optimization technique, which is guaranteed to have no access violations using tree-aware metadata of XML schemas. The scheme can be applied to any XML database management system and has several advantages such as small execution time overhead, fine-grained controls, and safe and correct query modification. The experimental results clearly demonstrate the efficiency of the approach.

• The KIPS Transactions:PartD
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• v.12D no.5 s.101
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• pp.773-780
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• 2005

If XML queries are expanded based on ontology, broader search may be possible. On the other hand, queries that are not adequate to target documents may also degrade the search efficiency. We try to improve query adequacy by expanding query based on a reduced ontology, which is the result of ontology and target DTD match. The match considers ontology concepts and DTD elements as well as ontology and DTD attributes. Since the reduced ontology can improve the hit ratio of queries and also be successively reusable for XML documents of a kind, the proposed method can improve XML search efficiency.

• The KIPS Transactions:PartD
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• v.13D no.4 s.107
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• pp.501-512
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• 2006

XML is the most popular platform-independent data expression which is used to communicate between loosely coupled heterogeneous systems such as B2B Applications or Workflow systems. The powerful query language XQuery has been developed to support diverse needs for querying XML documents. XQuery is designed to configure results from diverse data sources into a uniquely structured query result. Therefore, it became the standard for the XML query language. Although the latest XQuery supports heavy search functions including iterations, the grouping mechanism for data is too primitive and makes the query expression difficult and complex. Therefore, this work is focused on supporting the groupby clause in the query expression to process XQuery grouping. We suggest it to be a more efficient way to process grouping for restructuring and aggregation functions on XML data. We propose an XQuery EBNF that includes the groupby clause and implemented an XQuery processing system with grouping functions based on the eXist Native XML Database.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.183-194
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• 2004

As XML is a do facto standard for a data exchange language, there have been several researches on efficient processing XML queries. The most important thing to consider when processing XML queries is how efficiently we can process path expressions in queries. Some previous works make results by performing a sequence of join operations on all records corresponding to labels in the path expression. Others works check the existence of paths in the query using an RDBMS's string comparison operator and make results by extracting the records corresponding to the paths. In this paper we suggested a new query planning algorithm based on path containment relationships and two join operators supporting the planning algorithm. The join operators use only the records related to the paths in a query as input data, scan them only once, and generate result data using a pipelining mechanism. By analysis and experiments, we confirmed that our techniques(a new query planning algorithm and two join operators) achieved significantly higher performance than other previous works.

• Journal of KIISE:Databases
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• v.33 no.2
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• pp.224-238
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• 2006

As XML became the standard of data exchange in the internet, the needs for effective query processing for XML data in streaming environment is increasing. Applying the existing database technique which processes data with the unit of tuple to the streaming XML data causes the out-of-memory problem due to limited memory volume. Likewise the cost for searching query path and accessing specific data may be remarkably increased because of special structure of XML. In a word it is unreasonable to apply the existing database system to the streaming environment that processes query for partial data, not the whole one. Thus, it should be able to search partial streaming data that rapidly satisfies join predicate through using low-capacity memory, based on a store technique suitable to streaming XML data. In this thesis, in order to study the store technique for low-capacity memory, the PCDATA and the CDATA-related parts, which can be used as predicate on join query, were fetched and saved. In addition, in an attempt to compare rapid join predicates, the range window of streaming XML data was set with the object of selectively joining windows that satisfies the query, based on Cardinality * and + among the structure information of DTD.

• Journal of KIISE:Databases
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• v.35 no.1
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• pp.67-83
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• 2008

In order to realize ubiquitous computing, it is essential to efficiently use the resources and the computing power of mobile devices. Among others, memory efficiency, energy efficiency, and processing efficiency are required in executing the softwares embedded in mobile devices. In this paper, query processing over XML data in a mobile device where resources are limited is addressed. In a device with limited amount of memory, the techniques of XML. stream query processing need to be employed to process queries over a large volume of XML data Recently, a technique Galled XFrag was proposed whereby XML data is fragmented with the hole-filler model and streamed in fragments for processing. With XFrag, query processing is possible in the mobile device with limited memory without reconstructing the XML data out of its fragment stream. With the hole-filler model, however, memory efficiency is not high because the additional information on holes and fillers needs to be stored. In this paper, we propose a new technique called XFLab whereby XML data is fragmented with the XML labeling scheme which is for representing the structural relationship in XML data, and streamed in fragments for processing. Through implementation and experiments, XML showed that our XFLab outperformed XFrag both in memory usage and processing time.

• The KIPS Transactions:PartD
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• v.9D no.3
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• pp.381-388
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• 2002

XML documents, which are becoming new standard for expressing and exchanging data in the Internet, don't have defined schema. It is not adequate to directly apply XML documents to the existing SQL or OQL. Research on how to extract Schema for XML documents and query language is going on actively. For users' query, the results could be too tony or too less. It Is important to give the users adequate results. This paper suggests the way to extract many levelized schema according to the frequency of element occurrence in XML documents. The Schema can be reduced or extended to correspond to the users' query more flexibly.

• The KIPS Transactions:PartD
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• v.11D no.2
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• pp.293-304
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• 2004

Recently, caching for the database-backed web applications has received much attention. The results of frequent queries could be cached for repeated reuse or for efficient processing of the relevant queries. Since the emergence of XML as a standard for data exchange on the web, today's web applications are to retrieve information from the remote XML sources across the network, and thus it is desirable to maintain the XML query results in the cache for the web applications. In this paper, we describe implementation of an XML query processing system that supports cache-answerability of XML queries, and evaluate its performance. XML path expression, which is one of the core features of XML query languages including XQuery, XPath, and XQL was considered as the XML query. Their result is maintained as an XML materialized view in the XML cache. The algorithms to rewrite the given XML path expression using its relevant materialized view proposed in [13] were implemented with RDBMS as XML store. The major issues of implementation are described in detail. The results of performance experiments conducted with the implemented system showed effectiveness of cache-answerability of XML queries. Comparison with previous research in terms of performance is also Provided.