Converse approximation and rule extraction from decision tables in rough set theory
✍ Scribed by Yuhua Qian; Jiye Liang; Chuangyin Dang
- Publisher
- Elsevier Science
- Year
- 2008
- Tongue
- English
- Weight
- 278 KB
- Volume
- 55
- Category
- Article
- ISSN
- 0898-1221
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✦ Synopsis
In this paper, the concept of a granulation order is proposed in an information system. The converse approximation of a target concept under a granulation order is defined and some of its important properties are obtained, which can be used to characterize the structure of a set approximation. For a subset of the universe in an information system, its converge degree is monotonously increasing under a granulation order. This means that a proper family of granulations can be chosen for a target concept approximation according to user requirements. As an application of the converse approximation, an algorithm based on the converse approximation called REBCA is designed for decision-rule extraction from a decision table, which has a time complexity of O( m 2 |C| 2 |U |log 2 |U |), and its practical applications are illustrated by two examples.