Paradigm in the principle of database

recently about the heart of self-examination always have a little heart unwilling! Today I think of a few patterns that have been vague but curious! Think about how many times we mentioned it before. A few days to summarize this part! A little superficial, I think I have a lot of harvest. The following is a simple illustration of a picture.

make sense of how to judge whether it is a non-destructive decomposition. So, a textbook example shows (P79 example 3.11)

Set the relationship mode R (ABCD), R decomposition into Ρ={AB,BC,CD}. If the function dependency set established on R is F1={b→a,c→d}, will the ρ be decomposed with respect to F1? What if the function dependency set set up on R is f2={a→b,c→d}?

Explanation: Non-destructive decomposition is a row is all a, called non-destructive decomposition.

My understanding is this, b→a, can think of a as b as long as the left side of the AB has the same can be written as a (n). If there is not the same, it can only be written in B (i,j) Form. So there is a line of all a can be said to be non-destructive decomposition!