• Journal of KIISE:Software and Applications
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• v.30 no.1_2
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• pp.140-152
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• 2003

An XML document has a structure which may be irregular. It is difficult for end-users to comprehend the irregular document structure exactly. For these XML documents, an end-user has a difficulty in using structured query. Therefore, an end-user formulates no structured query or a query which has a little structure information. In this context, we propose new retrieval models which use the structured information for ranking and compensate the difference between user query structure and document structure. To ease with querying, we assume the independence among querying paths which represent structural constraints. Since this assumption makes degradation of the expression power of a query language, we also propose a model which overcome this problem. As there had been no test collections for XML documents, we made a small test collection from TIPSTER of the RTEC and experimented on this collection without a structured query, From this experiment, we showed that our models improve average precision about 67% over conventional Vector-Space model.

• 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.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11S
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• pp.3623-3632
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• 2000

Until now the XML document is allowed users to access the whole content of it However, for some applications such as those in the field of electronic commerce, there are cases that the whole content should not be delivered. Therefore, access authorization is required for XML documents in order to protect illegal accesses to some critical parts of them. In this paper. we design and implement a system which authorizes users to XML documents and controls access to them based on the access rights. We set the user group as a basic unit of the authorization subject and the element of an XML document as a basic unit of authorization object The owner of a document authorize; user groups to access the elements of it When an XML document is accessed, the access rights of the requester are checked using an access control list and only the authorized parts are delivered_ As the result, we can authorize XML documents, which has been previously impossible.

• Journal of KIISE:Databases
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• v.35 no.4
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• pp.307-318
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• 2008

One of the primary issues confronting XML message brokers is the difficulty associated with processing a large set of continuous XPath queries over incoming XML seams. This paper proposes a novel system designed to present an effective solution to this problem. The proposed system transforms multiple XPath queries before their run-time into a new region-based data structure, called an XP-table, by sharing their common constraints. An XP-table is matched with a stream relation (SR) transformed from a target XML stream by a SAX parser. This arrangement is intended to minimize the runtime workload of continuous query processing. Also, system performance is estimated and verified through a variety of experiments, including comparisons with previous approaches such as YFilter and LazyDFA. The proposed system is practically linear- scalable and stable for evaluating a set of XPath queries in a continuous and timely fashion.

• Annual Conference of KIPS
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• 2005.05a
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• pp.687-690
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• 2005

최근 들어 무선인터넷 단말기로 보다 효율적으로 인터넷에 접근하여 정보를 제공하고자 하는 연구가 활발히 진행되고 있다. 사용자는 유선 인터넷으로 제공받는 컨텐츠를 휴대가 간편한 무선 이동통신으로 제공받고자 하는 욕구가 점점 늘어나고 있고 이러한 원인으로 다양한 무선 컨텐츠의 제공이 요구된다. 그러나 다양한 무선 단말기의 특성에 따라 컨텐츠를 새롭게 개발하는데는 개발비용, 기간이 많이 들게 되므로 기존의 웹 컨텐츠를 활용하여 무선환경에 맞는 문서변환 기술 연구의 필요성이 대두되고 있다. 본 논문에서는 유선 인터넷상의 컨텐츠를 무선 환경으로 손쉽게 변환할 수 있는 XML(eXensible Markup Language)기술을 활용한 변환기(Generator)구조를 설계하고 이와 관련된 XML Generator, RuleSet Management, Clipping Toolkit 등의 기능을 정의하여 보다 효율적으로 무선 컨텐츠로 변환하는 기술을 소개한다.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.326-333
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• 2005

Many XML applications use XPath Patterns as a query language for XML documents. Two XPath patterns may have containment relationship, and the containment problem between two XPath patterns is a problem that determines whether one XPath pattern contains another XPath Pattern. Although the containment problem occurs in many applications, it is known as a co-NP complete. A homomorphism problem, which is a sufficient condition for the containment problem, is solved in polynomial time. We first discuss applications that replace the containment problem with the homomorphism problem, and maintaining homomorphism information among XPath patterns will benefit those applications. Then, we propose a lattice structure, called POX (Partially Ordered Set of XPath Patterns), and develop algorithms for maintaining it. As our analyses show, the algorithms can efficiently maintain POX in polynomial time.

• Journal of Korea Multimedia Society
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• v.7 no.9
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• pp.1208-1218
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• 2004

Nowadays the information exchange based on XML such as B2B electronic commerce is spreading. Therefore a systematic and stable management mechanism for storing the exchanged information is needed. For this goal there are many research activities for centering on relational databases the connection between XML application and databases. But when XML data which has hierarchical structure is stored as relational databases which are expressed as relational information, a set of 2-dimensional table, there is a limitation essentially. Accordingly the modeling methodology for storing such structured information in the form of object-relational databases is needed. In order to build good quality application systems, modeling is an important first step. In 1997, the OMG adopted the UML as its standard modeling language. Since industry has warmly embraced UML, its popularity should become more important in the future. So a design methodology based on UML is needed to develop efficient XML applications. In this paper, we propose a unified design methodology for XML applications based on object-relational database using UML. To reach these goals, first we propose a systematic three step methodology to extract UML, second we introduce a XML modeling methodology to design W3C XML schema using UML and third we propose a data modeling methodology for object-relational database schema to store exchanging XML data efficiently.

• The KIPS Transactions:PartD
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• v.10D no.3
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• pp.387-398
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• 2003

Materialized views have received much attention for query performance improvement. They need to be refreshed whenever their underlying data sources are updated. They could be recomputed from scratch or they could be incrementally refreshed by reflecting only those portions of updates that affect them. With emergence of XML as the standard for data exchange on the Web, active research is under way on effectively storing and retrieving XML documents. In this paper, we describe a performance study on the incremental refresh of XML materialized views for the case where XML documents are stored in a relational DBMS, and XML materialized views are maintained with incremental refresh. We describe implementation of a prototype XML storage system that supports XML materialized views and their incremental refresh, and report the performance results obtained with the implemented system through a detailed set of experiments on the incremental refresh of XML materialized views. The results show that the XML view maintenance with incremental refresh outperforms the ordinary view recomputation.

• Journal of KIISE:Databases
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• v.32 no.2
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• pp.177-192
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• 2005

In this paper, we introduce a structural redundancy method. It reduces the query processing cost incurred when reconfiguring an XML document from divided XML data in shredding XML documents into relations. The fundamental idea is that query performance can be enhanced by analyzing query patterns and replicating data essential for the query performance. For the practical and effective structural redundancy, we analyzed three types of ID, VALUE, and SUBTREE replication. In addition, if given XML data and queries are very large and complex, it can be very difficult to search optimal redundancy set. Therefore, a heuristic search method is introduced in this paper. Finally, XML query processing cost arising by employing the structural redundancy, and the efficiency of proposed search method arc analyzed experimentally It is manifest that XML read query is performed more quick]y but XML update query is performed more slowly due to the additional update consistency cost for replicas. However, experimental results showed that in-place ID replication is useful even in having excessive update cost. It was also observed that multiple-place SUBTREE replication can enhance read query performance remarkably if only update cost is not excessive.

• Journal of the Korea Society of Computer and Information
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• v.13 no.4
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• pp.71-78
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• 2008

Digital Broadcasting serves a variety of broadcasting services for satisfying the requirement of customers. One of main factors for new broadcasting environment is interoperability between providers and consumers. For this interoperability, metadata standards are proposed for the digital broadcasting and TV-Anytime metadata is one of these standards. On the one hand, there are some researches for efficiently managing the broadcasting metadata on Set-Top Box. This paper proposes the metadata management system for efficiently managing the broadcasting metadata based on the STB which is low-cost and low-setting. Our system consists of a storage engine to store the metadata and an XQuery engine to search the stored metadata and uses special index for storing and searching. We expect that our system will keep the interoperability amongst a variety of applications for broadcasting because we adopts the XQuery for searching the metadata and the XQuery is a standard language for searching XML data.