• Journal of the Korean Society for information Management
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• v.30 no.2
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• pp.297-315
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• 2013

This study aims to analyze and evaluate term suggestion services of major search portals, Naver and Google Korea. In particular, this study evaluated relevance and currency of related search terms provided, and analyzed characteristics such as number and distribution of terms, and queries that did not produce terms. This study also analyzed types of terms in terms of the relationship between queries and terms, and investigated types and characteristics of harmful terms and terms with grammatical errors. Finally, Korean queries and English queries, and popular queries and academic queries were compared in terms of the amount and relevance of search terms provided. The results of this study show that the relevance and currency of Naver's related search terms are somewhat higher than those of Google. Both Naver and Google tend to add terms to or delete terms from original queries, and provide identical search terms or synonym terms rather than providing entirely new search terms. The results of this study can be implemented to the portal's effective development of term suggestion services.

• Journal of KIISE:Databases
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• v.35 no.3
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• pp.231-242
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• 2008

W3C has selected OWL as a standard for Web ontology description and a necessity of research on storage models that can store OWL ontologies effectively has been issued. Until now, relational model-based storage systems such as Jena, Sesame, and DLDB, have been developed, but there still remain several issues. Especially, they lead inefficient query processing performance. The structural problems of their low query processing performance are as follow: Jena has a simple structure which is not normalized and also stores most information in a single table. It exponentially decreases the performance because of comparison with unnecessary information for processing queries requiring join operations as well as simple search. The structures of storages(e.g., Sesame) have been completely normalized. Therefore it executes many join operations for query processing. The storages require many join operations to find simply a specific class. This paper proposes a storage model to resolve the problems that the query processing performance is decreased because of non-normalization or complete normalization of the existing storages. To achieve this goal, we analyze the problems of existing storage models as well as relations of OWL elements and query patterns. The proposed model, defined with the analysis results, provides an optimal normalized structure to minimize join operations or unnecessary information comparison. For the experiment of query processing performance, a LUBM data sets are used and query patterns are defined considering search targets and their hierarchical relations. In addition, this paper conducts experiments on correctness and completeness of query results to verify data loss of the proposed model, and the results are described. With the comparative evaluation results, our proposal showed a better performance than the existing storage models.

• Journal of KIISE:Databases
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• v.29 no.4
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• pp.247-261
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• 2002

Aggregation is an important operation that affects the performance of OLAP systems. In this paper we define a new class of aggregation queries, called range-groupby queries, and present a method for processing them. A range-groupby query is defined as a query that, for an arbitrarily specified region of an n-dimensional cube, computes aggregations for each combination of values of the grouping attributes. Range-groupby queries are used very frequently in analyzing information in MOLAP since they allow us to summarize various trends in an arbitrarily specified subregion of the domain space. In MOLAP applications, in order to improve the performance of query processing, a method of maintaining precomputed aggregation results, called the prefix-sum array, is widely used. For the case of range-groupby queries, however, maintaining precomputed aggregation results for each combination of the grouping attributes incurs enormous storage overhead. Here, we propose a fast algorithm that can compute range-groupby queries with minimal storage overhead. Our algorithm maintains only one prefix-sum away and still effectively processes range-groupby queries for all possible combinations of the grouping attributes. Compared with the method that maintains a prefix-sum array for each combination of the grouping attributes in an n-dimensional cube, our algorithm reduces the space overhead by (equation omitted), while accessing a similar number of cells.

• Journal of Information Management
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• v.39 no.3
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• pp.163-177
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• 2008

In this paper, we analyzed the relationship between user query keywords that is used to search NDSL and technical terms extracted from NDSL journals. For the analysis, we extracted about 833,000 query keywords from NDSL search logs during nearly 17 months and approximately 41,000,000 technical terms from NDSL, INSPEC, FSTA journals. And we used only the English noun phrase in extracted those and then we did an experiment on analysis of equality, relationship analysis and frequency analysis.

• Journal of the Korea Computer Industry Society
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• v.5 no.9
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• pp.1111-1118
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• 2004

Natural language query is the best user interface for the users of web text retrieval systems. This paper proposes a retrieval system with expanded keyword from syntactically-analyzed structures of user's natural language query based on natural language processing technique. Through the steps combining or splitting the compound nouns based on syntactic tree traversal, and expanding the other-formed or shorten-formed keyword into multiple keyword, it shows that precision and correctness of the retrieval system was enhanced.

• Journal of the Korean Society for information Management
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• v.21 no.2
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• pp.235-248
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• 2004

For the users of information retrieval systems, natural language query is the more ideal interface, compared with keyword and boolean expressions. This paper proposes a retrieval technique with expanded keyword from syntactically-analyzed structures of natural language query as user input. Through the steps combining or splitting the compound nouns based on syntactic tree traversal of the query, and expanding the other-formed or shorten-formed into multiple keyword, it can enhance the precision and correctness of the retrieval system.

• Journal of KIISE:Databases
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• v.28 no.2
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• pp.168-180
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• 2001

데이터 웨어하우스 시스템에 대한 OLAP 질의들은 대량의 데이터를 대상으로 복잡한 분석 및 집계 연산을 수행한다. 이러한 고비용의 OLAP 질의들을 효율적으로 실행하는 것은 시 스템의 성능 향상을 위해 매우 중요하다. 이를 위해 본 논문에서는 데이터 웨어하우스 시스 템에 존재하는 여러 종류의 실체 집계 뷰들을 이용하여 주어진 OLAP 질의를 재작성하는 방법을 제안한다. 본 논문에서는 차원 계층들로부터 유도되는 그룹 격자를 이용하여 OLAP 질의와 실체 뷰의 선택 단위, 선택 영역, 집계 단위등을 정의하고, 이들로부터 OLAP 질의 와 식체 뷰에 대한 정규을 정의한다. 그리고 정규형으로 표현된 질의와 실체 뷰 사이의 관 계를 이용하여 실체 뷰가 질의의 재작성에 이용 가능하기 위한 조건을 제시한다. 제안하는 질의 재작성 방법은 데이터 웨어하우스의 메타 정보들과 OLAP 질의 및 실체 뷰들의 특성 을 고려하여 다양한 실체 뷰들을 함께 이용할 수 있으므로, 시스템에 존재하는 실체 뷰들의 효용성을 높이고 주어진 질의를 효율적으로 처리할 수 있다.

• The KIPS Transactions:PartD
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• v.16D no.3
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• pp.295-306
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• 2009

Query execution time minimization is an important objective in distributed database design. While total time minimization is an objective for On Line Transaction Processing (OLTP), response time minimization is for Decision Support queries. We formulate the sub-query allocation problem using analytical models and solve with genetic algorithm (GA). We show that query execution plans with total time minimization objective are inefficient from response time perspective and vice versa. The procedure is tested with simulation experiments for queries of up to 20 joins. Comparison with exhaustive enumeration indicates that GA produced optimal solutions in all cases in much less time.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10b
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• pp.173-175
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• 2000

본 연구에서는 전자상거래 데이터베이스를 대상으로 결합범주문법을 이용한 자연언어질의 인터페이스를 구현한다. 이를 위해 질의문을 분석하고 표현 방법을 논의한다. 또한 SQL 형식언어로 변환하기 위한 어휘 표현 및 유도 방법을 보인다. 제안하는 방법은 구문분석 과정에서 SQL 형식의 질의문을 직접 유도하는 것으로 기존 연구에서 제안됐던 중간논리언어 변환단계를 거치지 않으므로 과정이 간결해져 시스템의 성능향상을 가져올 수 있다. 시스템은 웹 기반과 client/server 구조로 구현된다.

• 산업보건소식
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• no.42
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• pp.21-25
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• 1987

산업이 다양화.고도화됨에 따라 생산공정중에 불가피하게 발생되는 수많은 유해물질의 포집, 분석 방법에 대하여 우리실정에 알맞는 표준방법을 정함으로써 사업장 유해환경측정에 참고가 되고 나아가서 작업환경측정방법의 일원화를 도모하고자 노동부 국립노동과학연구소에서 수년간에 걸쳐 비교 연구하여 최근 보고한 바 있는 유해물질의 표준 실험 방법을 소개하고자 한다.