functional dependency

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functional dependency

(database)
Given a relation R (in a relational database), attribute Y of R is functionally dependent on attribute X of R and X of R functionally determines Y of R (in symbols R.X -> R.Y) if and only if each X in R has associated with it precisely one Y in R (at any one time). Attributes X and Y may be composite.

This is very close to a function in the mathematical sense.
This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

functional dependency

A dependent relationship between two data elements in a relational database. Used to define normalization, a functional dependency (FD) states that one data element is dependent on another. For example, a social security number (SSN) refers to only one employee (EMP). Expressed as SSN->EMP, employee is dependent on social security number. A product number refers to one product (PRODNO->PRODNAME), and a customer number refers to one customer name (CUSTNO->CUSTNAME). See normalization and transitive dependency.
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This work was supported by the Pan American Health Organization (PAHO Grant BRA/3176), the Fundacao de Desenvolvimento da Pesquisa (FUNDEP, subproject 10/99), and the Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES, BEX 3201/ 040).
In relation to the river Sao Francisco, Emas is in better fishing conditions when compared to the data of the Fisher's Colony of Pirapora (MG) Z-1, where they caught 11.7 kg/fisher/day in 1987 (Godinho et al., 1997) and in 1999 only 3.1 kg/fisher/day (Fundep, 2000 apud Godinho and Godinho, 2003).