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What is Functional dependency

Chapter 24
Handbook of Research on Fuzzy Information Processing in Databases
A functional dependency states that the value of an attribute is uniquely determined by the values of some other attributes.
Published in Chapter:
Incremental Discovery of Fuzzy Functional Dependencies
Shyue-Liang Wang (New York Institute of Technology, USA), Ju-Wen Shen (Chunghwa Telecom Lab, Taiwan), and Tuzng-Pei Hong (National University of Kaohsiung, Taiwan)
Copyright: © 2008 |Pages: 19
DOI: 10.4018/978-1-59904-853-6.ch024
Abstract
Mining functional dependencies (FDs) from databases has been identified as an important database analysis technique. It has received considerable research interest in recent years. However, most current data mining techniques for determining functional dependencies deal only with crisp databases. Although various forms of fuzzy functional dependencies (FFDs) have been proposed for fuzzy databases, they emphasized conceptual viewpoints and only a few mining algorithms are given. In this research, we propose methods to validate and incrementally search for FFDs from similarity-based fuzzy relational databases. For a given pair of attributes, the validation of FFDs is based on fuzzy projection and fuzzy selection operations. In addition, the property that FFDs are monotonic in the sense that r1 ? r2 implies FDa(r1) ? FDa(r2) is shown. An incremental search algorithm for FFDs based on this property is then presented. Experimental results showing the behavior of the search algorithm are discussed.
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Chapter 22
Imprecise Functional Dependencies
Given two sets of attributes X and Y, a functional dependency between them is denoted by X ? Y. The constraint says that, for any two tuples t1 and t2 having t1[X] = t2[X], then t1[Y] = t2[Y]. More precisely, given a table R, X ? Y ? ?t1, t2 ? R.(t1[X] = t2[X] ? t1[Y] = t2[Y]).
Published in Chapter: Imprecise Functional Dependencies; From: Handbook of Research on Innovations in Database Technologies and Applications: Current and Future Trends
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Chapter 22
Applying Fuzzy Data Mining to Tourism Area
In the regular case, a functional dependency, denoted by X? Y, expresses that a function exists between the two sets of attributes X and Y, and it can be stated as follows: For any pair of tuples t1 and t2, if t1 and t2 have an equal value on X, they also have the same value on Y.
Published in Chapter: Applying Fuzzy Data Mining to Tourism Area; From: Handbook of Research on Fuzzy Information Processing in Databases
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Chapter 39
Merging, Repairing, and Querying Inconsistent Databases
A functional dependency is a constraint between two sets of attributes in a relation from a database. Given a relation R, a set of attributes X in R is said to functionally determine another attribute Y, also in R (written X ? Y) if and only if each X value is associated with at most one Y value.
Published in Chapter: Merging, Repairing, and Querying Inconsistent Databases; From: Handbook of Research on Innovations in Database Technologies and Applications: Current and Future Trends
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Chapter 25
Data Dependencies in Codd's Relational Model with Similarities
Functional dependency is a formula where A and B are collections of attributes. being true in a table means that every two rows of a table that have the same values on attributes from A have the same values on attributes from B. Functional dependencies play important roles in the design of relational databases.
Published in Chapter: Data Dependencies in Codd's Relational Model with Similarities; From: Handbook of Research on Fuzzy Information Processing in Databases
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Chapter 13
Interrogative Agents for Data Modeling
Given two sets of attributes X and Y, a functional dependency between them is denoted by X ? Y. The constraint says that, for any two tuples t1 and t2 having t1[X] = t2[X], then t1[Y] = t2[Y]. More precisely, given a table R, X ? Y ? ?t1, t2 ? R.(t1[X] = t2[X] ? t1[Y] = t2[Y]).
Published in Chapter: Interrogative Agents for Data Modeling; From: Handbook of Research on Innovations in Database Technologies and Applications: Current and Future Trends
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Chapter 21
Identifying Batch Processing Features in Workflows
Functional dependencies are relationship between attributes of a database relation: a functional dependency states that the value of an attribute is uniquely determined by the values of some other attributes.
Published in Chapter: Identifying Batch Processing Features in Workflows; From: Handbook of Research on Complex Dynamic Process Management: Techniques for Adaptability in Turbulent Environments
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