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Sampling Effectiveness in Discovering Functional Relationships in Databases
Published in Takushi Tanaka, Setsuo Ohsuga, Moonis Ali, Industrial and Engineering Applications of Artificial Intelligence and Expert Systems, 2022
Atsuhiro Takasu, Tatsuya Akutsu, Moonis Ali
We have been studying sampling effectiveness to discover functional relationships in databases. This relationship is a fundamental regularity and it is generally used as a constraint that databases should obey. As a constraint, it is called functional dependency (FD) and is used to design and maintain the consistency of relational databases [U188]. Hereafter the terms functional dependency and functional relationship are used interchangeably and abbreviated to FD. As a constraint, the exact FD is used. The FD is useful as a rule too. It can be used, for example, in query processing and guessing unknown values in distributed databases. As a rule, the exact FD is too strict since it does not allow any exceptions, but the approximate FD has broader applications. In our previous work [AT92, AT93], we analyzed the sampling effectiveness theoretically and showed the necessary size of a sample in order to extract FDs from samples. In this paper, we confirm the theoretical result through several experiments using a very large database containing bibliographic information about books and journals stored in Japanese universities. Furthermore, we discuss the effectiveness in finding FDs that are approximately correct in the original database.
F
Published in Phillip A. Laplante, Dictionary of Computer Science, Engineering, and Technology, 2017
functional dependency a relationship between attributes in database systems. Given attributes A and B, a functional dependency exists between A and B, if and only if there is only one value of A for any given B. We say B is functionally dependent on A. We say A functionally determines B. A functional dependency between A and B is denoted by A → B.
Parameterized simplification logic I: reasoning with implications and classes of closure operators
Published in International Journal of General Systems, 2020
Pablo Cordero, Manuel Enciso, Angel Mora, Vilem Vychodil
In relational databases (Maier 1983), a functional dependency is a formula of the form , where A and B are subsets of attributes of a (finite) relation schema. For our purposes, a relation schema can be seen as a finite set R of attributes. Syntactically, functional dependencies are the same formulas as attribute implications from Example 4.7, however, they are interpreted in relations on relation schemes. In formalization of functional dependencies and their semantics in our logic, we can proceed in much the same way as in Example 4.7. In fact, using the result from Fagin (1977) and Sagiv et al. (1981), the relationship comes almost immediately using our observations from Example 4.7.