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The Study of Rough Data Querying Based on RRDB

Author: HuXingLei
Tutor: HongXiaoGuang
School: Shandong University
Course: Computer Software and Theory
Keywords: Rough Set Rough relational database Rough data query
CLC: TP311.13
Type: Master's thesis
Year: 2008
Downloads: 63
Quote: 1
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Abstract


1982, the Polish scholar Z.Pawlak proposed rough set theory A characterization of incompleteness and uncertainty of mathematical tools to effectively analyze incomplete information. He established a classification mechanism based on the knowledge base of known (approximate) to characterize imprecise or uncertain knowledge. The theory and the other to deal with uncertain and imprecise theory on the most significant difference is that it does not need to provide the required processing of data collection outside any a priori information. Beaubouef.T rough set theory and the traditional relational database model combining proposed rough relational database model (RRDM) concept to describe the the uncertainty information systems. The RRDM ordinary relational database model is the same, in many respects, the main difference is the values ??of its properties can have a plurality of atomic values ??constitute, but unlike the relational database is a single attribute value, so RRDM is actually a multi-value information systems. RRDM is a combination of some of the basic concepts of rough set theory, such as the equivalence class, upper approximation, lower approximation and some of the basic theory of relational databases, it is the extension of the standard relational database model, it is in order to enhance the relational database information The ability to express and raised. Data query is the core operation of the database system, rough relational database query called rough data querying, rough data querying into three categories: precise queries, rough full query and rough combination of queries. At present, many domestic and foreign scholars study on the problem of how to achieve rough data query, their common feature is a complete query semantic equivalence relation on the attribute range expansion of the original selection criteria on the increase due to the expanded selection criteria The judgment of the semantics of the same value, to reduce the query efficiency. In this paper, the problems of rough data querying achieve proposed query bit vector encoding based implementations. First the the multivalued data encoded as a single bit vector code value, only need query processing encoded value judgments, without considering the semantic relationships on the original attribute range, thus simplifying the rough data query semantic relations on the attribute range realization, to improve query efficiency. At the same time, this query is based on standard SQL statements rough relational database functionality, practicality existing relational database. The main work of this paper are: 1. Proposed bit vector encoded query-based implementations, and gives a bit vector encoding algorithm and bit vector code value in maintenance algorithm. 2 for three different types of rough data query, given the specific implementations based on the bit vector encoding. Designed corresponding experiment with the existing query implementation methods were compared. Through the analysis of the experimental results, we draw some useful conclusions.

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CLC: > Industrial Technology > Automation technology,computer technology > Computing technology,computer technology > Computer software > Program design,software engineering > Programming > Database theory and systems
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