Relaxing Queries by Combining Knowledge Abstraction and Semantic Distance Approach

The study on query relaxation which provides approximate answers has received attention. In recent years, some arguments have been made that semantic relationships are useful to present the relationships among data values and calculating the semantic distance between two data values can be used as a quantitative measure to express relative distance. The aim of this article is a hierarchical metricized knowledge abstraction (HiMKA) with an emphasis on combining data abstraction hierarchy and distance measure among data values. We propose the operations and the query ralxation algorithm appropriate to the HiMKA. With various experiments and comparison with other method, we show that the HiMKA is very useful for the quantified approximate query answering and our result is to offer a new methodological framework for query relaxation.

Extension and enhancement of storage system MIDAS

학위논문(석사) - 한국과학기술원 : 전산학과, 1994.2, [ 1책(면수복잡) ]한국과학기술원 : 전산학과

지식추상화 및 고차원 자료 인덱스를 이용한 협력적 질의 처리기 설계

학위논문(박사) - 한국과학기술원 : 경영공학전공, 2006.2, [ ix, 116 p. ]As databases get more and more complex, exact answers of queries by the database alone get less and less helpful, and hence the ability of the database system to cooperate with the user is emphasized. The purpose of Cooperative query answering, in database systems, is to provide relevant information of a wider scope or even approximate answers as well as exact answers. Typical steps for the cooperative query answering consist of query analysis, query relaxation and provision of information that is relevant to or associated with the query. To facilitate the query relaxation, a knowledge representation framework has been widely adopted, which uses a data abstraction to represent semantic relationships, or which uses distance metric to represent quantitative similarities among data values. However, in terms of knowledge representation framework, previous studies on cooperative query answering have limitations in accommodating the data abstraction and distance metric together. In this dissertation, we design a query processor that accommodates the data abstraction and distance metric together to efficiently support cooperative query answering. First, we propose a metricized knowledge abstraction hierarchy (MKAH) that integrates multi-level data abstraction hierarchy with distance metric among data values. To develop the distance metric, we introduce basic distance that is assigned between two directly linked nodes in the MKAH, and the distance between two arbitrary nodes is calculated by incorporating the basic distances. The calculated distances are grouped by level differences, and they are precisely discriminated according to the similarity. In terms of cooperative query answering, the MAKH can support more interactive and flexible query relaxation processes with the abstraction level information. Since the MKAH supports the distance metric, it is appropriate to handle the quantitative similarity of categorical data, and query results with the MKAH can be ranked...한국과학기술원 : 경영공학전공

Evaluation of density in layer compaction using SASW method

SASW test, which is non-intrusive and rapid in the field application, was used to evaluate the layer density in the roller compaction without performing the complicated inversion process. The concept of normalized shear wave velocity was introduced to minimize the effect of confinement in the density evaluation. SASW test was performed to determine the shear wave velocity of the layer, and the free-free resonant column (FF-RC) test was adopted to determine the correlation between the normalized shear wave velocity and density of the site, which is almost unique independent of confinement. Testing and data reduction procedures of both tests were briefly discussed and an evaluation procedure of the field density was proposed by effectively combining in-situ shear wave velocity determined by the SASW test with the correlation between the normalized shear wave velocity and the density determined by the FF-RC test. Finally, the feasibility of the proposed method was verified by performing a field case study at Hoengsung road construction site. Field densities determined by the proposed method matched well with those determined by sand cone tests, showing the potential of applying the proposed method in the field density evaluation. (C) 2001 Elsevier Science Ltd. All rights reserved