Properties of functional-dependency families
Seymour Ginsburg, Sami Mohammed Zaiddan · Journal of the ACM · 1982
A functional-dependency (FD-) family Is defined here as the family of all instances satisfying a set of functional dependencies These families are studied with respect to projection, join, and decomposition and their connection with generating families and generators Typical results obtained are (0 a charactenzauon for when the projection of an FD-family is an FD-family; 00 a charactenzauon for when the join of two FD-famihes is an FD-famdy, (m) a necessary and sufficient condition for an F D-famdy to be decomposable; and 0v) that every domam-infmlte FD-family has a generatorOne surpnsmg conclusion of this study is that there seems to be a considerable difference between the case in which each domain is relatively large with respect to the number of domains considered and the case m wluch some of the domains are relatively small.