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.

(1997-09-01)