For the attribute set R=BCEGVWY, let the MVDs be:
R = WBCY ./ YEVG
R =WBCE ./ WBYVG
R =WBY ./ CYEVG
Find a lossless decomposition into 4NF. Is it unique?
Use MVD #1 to obtain the following decomposition: WBCY, YEVG. MVD #2 applies to
WBCY and yields WBC, WBY. MVD #3 cannot be used to decompose WBC because the join
attribute, Y, is not in this attribute set. It cannot be used to decompose WBY or YEVG because
MVD #3 projects as a trivial dependency in these cases: WBY = WBY ./ Y and YEVG = Y ./
YEVG. Thus, the result is WBC, WBY, YEVG.
The above decomposition is not unique. If we rst apply MVD #3 and then #1 then will obtain
the following result: WBY, CY, YEVG.
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