Closure of a set of functional dependency

Question

I am little bit confused about the CLOSURE OF A SET-OF-FUNCTIONAL-DEPENDENCIES .

If I am given a set of Functional dependencies F, then how the F⁺ is defined ?

• Is it defined as the union of the closures of LHS of each of FD within F 
• Or is it calculated as set of all valid functional dependencies (including the additional functional dependencies - which are calculated from inference rules)

I am following Navathe 6th edition and here they have given procedure to calculate the closure of LHS of FD within a set of FD's, however, I did not find any procedure to find out the closure of the set of FDs.

Thank You

Comments

by the both procedure you can get the same result...

if you are confusing how these two are equal... Just think you are using attribute closure for finding additional functional dependencies directly right?