• Proceedings of the Korean Information Science Society Conference
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• 2004.04b
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• pp.136-138
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• 2004

XML 이 웹 상에서의 정보 표현, 통합, 교환을 위한 표준이 됨에 따라 다양한 XML 질의 언어들이 제안되었으며, World Wide Web Consortium(W3C)은 XQery를 XML 질의 언어의 표준으로 권고하였다. XQuery는 SQL과 유사하게 중첩 질의를 허용하므로, 중첩된 XQuery 질의를 동일한 의미를 가지면서 보다 효율적으로 실행될 수 있는 질의로 변환하는 정규화 규칙들이 제안되었다. 그러나 제안된 정규화 규칙들은 제한적인 형태의 중첩 질의에만 적용되는 문제점을 가지고 있다 특히, FLWR 표현식의 where 절에 있는 중첩을 처리할 수 없다. 본 논문에서는 SQL 질의의 정규화 규칙들을 확장하여 FLWR 표현식의 모든 절에 나타나는 중첩을 처리할 수 있는 XQuery 질의의 정규화 규칙들을 제안한다 이를 위해 먼저, 상관과 집계의 유무에 따라 XQuery 질의의 중첩 유형을 분류하고, 각 유형 별로 정규화 규칙들을 제안한다 다음으로, 중첩된 XQuery 질의에 정규화 규칙들을 적용하는 세부 알고리즘을 제안한다.

• Journal of KIISE:Computing Practices and Letters
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• v.10 no.5
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• pp.419-433
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• 2004

As XML becomes a standard for data representation, integration, and exchange on the Web, several XML query languages have been proposed. World Wide Web Consortium(W3C) has proposed XQuery as a standard for the XML query language. Like SQL, XQuery allows nested queries. Thus, normalization rules have been proposed to transform nested XQuery queries to semantically equivalent ones that could be executed more efficiently. However, previous normalization rules are applicable only to restricted forms of nested XQuery queries. Specifically, they can not handle FLWR expressions having nested expressions in the where clause. In this paper, we propose normalization rules for XQuery queries by extending those for SQL queries. Our proposed rules can handle FLWR expressions haying nested expressions in every clause. The major contributions of this paper are as follows. First, we classily nesting types of XQuery queries according to the existence of correlation and aggregation. We then propose normalization rules for each nesting type. Second, we propose detailed algorithms that apply the normalization rules to nested XQuery queries.

• Journal of the Korea Society of Computer and Information
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• v.14 no.3
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• pp.1-11
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• 2009

XQuery query proposed by W3C is one of the standard query languages for XML data and is widely accepted by many applications. Therefore the studies for efficient Processing of XQuery query have become a topic of critical importance recently and the optimization of XQuery query is one of new issues in these studies. However, previous researches just focus on the optimization techniques for a specific XML data management system and these optimization techniques can not be used under the any XML data management systems. Also, some previous researches use predefined XML data structure information such as XML schema or DTD for the optimization. In the real situation, however applications do not all refer to the structure information for XML data. Therefore, this paper analyzes only a XQuery query and optimize by using itself of the XQuery query. In this paper, we propose 3 kinds of optimization method that considers the characteristic of XQuery query. First method removes the redundant expressions described in XQuery query second method replaces the processing order of operation and clause in XQuery query and third method rewrites the XQuery query based on FOR clause. In case of third method, we consider FOR clause because generally FOR clause generates a loop in XQuery query and the loop often rises to execution frequency of redundant operation. Through a performance evaluation, we show that the processing time for rewritten queries is less than for original queries. also each method in our XQuery query optimizer can be used separately because the each method is independent.

• Proceedings of the Korean Information Science Society Conference
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• 2007.06c
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• pp.29-32
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• 2007

SQL은 관계형 DBMS에서 사용되는 표준 질의 언어이다. SQL의 장점 중의 하나는 중첩 질의의 사용이나, 중첩질의를 포함한 질의를 그대로 실행하는 것은 중첩 질의의 반복된 수행을 야기하여 비효율적이다. 본 논문에서는 SQL3 표준에 정의된 모든 유형의 중첩 질의에 대한 완전한 정규화 규칙을 제안한다. SQL3 표준에서 중첩질의는 중첩 질의 반환 값의 유형에 따라 스칼라 중첩 질의와 테이블 중첩 질의로 분류된다. 스칼라 중첩 질의와 테이블 중첩 질의는 상관과 집계의 유무에 따라 다시 분류될 수 있다. 본 논문에서는 SELECT, FROM, WHERE 절에서 이러한 분류에 의해 가능한 모든 중첩 유형을 지원한다. 특히, SELECT, FROM 절의 일부 중첩 유형은 SQL3와 유사한 형태의 중첩 질의를 지원하는 질의 언어인 XQuery에서 제안된 정규화 규칙을 SQL3 문법에 맞게 응용하여 적용한다.

• Journal of KIISE:Databases
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• v.34 no.6
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• pp.528-545
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• 2007

Recently ontology has been an attractive technology along with the business strategy of providing a plenty of more intelligent services. The essential problem in application domains using ontology is that all members, agents, and application programs in the domains must share the same ontology concepts. However, a variety of mobile devices, sensing devices, and network components manufactured by various companies, a variety of common carriers, and a variety of contents providers make multiple heterogeneous ontologies more likely to coexist. We can see many past researches fallen into resolving this semantic interoperability. Such methods can be broadly classified into by-mapping, by-merging, and by-translation. In this research, we focus on by-translation among them which uses a translation rule directly made between two heterogeneous ontology data like OntoMorph. However, the manual composition of the direct translation rule is not convenient by itself and if there are N ontologies, the direct method has the rule composition complexity of $O(N^2)$ in the worst case. Therefore, in this paper we introduce the cascade composition of translation rules based on web openness in order to improve the complexity. The research result made us recognize some important factors in an ontology translation system, that is speediness of translation, and conveniency of translation rule composition, and some experiments and comparing analysis with existing methods showed that our cascade method has more conveniency with insuring the speediness and the correctness.