查找一组函数依赖项的闭包

Question

使用Armstrong Axiom找到F +

R = {A，B，C，D}

功能依赖性= {A} - ＆gt; {B}，{B，C} - ＆gt; {d}

F+ = {A} --> {A,B} --> {B,C} --> {C,D} --> {D} 
     Derived from above using reflexivity: 
     {A} --> {B}, {A,B} --> {B}, {A,D} --> {B,D}, {A,C} --> {B,C}, {A,C,D} --> {B,C}
     Derived from above using augmentation:
     {A} --> {A,B}, {A,B} --> {A,B, A,D} --> {A,B,D}, {A,C} --> {A,B,C}, {A,C,D} --> {A,B,C,D}

     {B,C} --> {D}, {A,C} --> {D} (transitivity), {A,C} --> {A,B,C,D} (union rule)
     Derived from above using augmentation:
     {A,B,C} --> {A,D}, {A,B,C} --> {B,D}

我试图了解如何推导出F + 所以我已经添加了我如何得出它们。

但我不确定他们是否正确。

我感觉我错过了{B，C}的某些部分 - ＆gt;关闭内部{D}。