Closure of a set of Attributes
Given a set of attributes {A1, …, An} and a set of dependencies S.
Problem: find all attributes B such that:
any relation which satisfies S also satisfies:
A1,
…, An B
The
closure of {A1, …, An}, denoted {A1, …, An} ,
is
the set of all such attributes B
The closure tells us everything we can infer from
A1,…, An.
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