UML composition attributes not feature in the class?

Question

I have a class A and it has data members of class B and class C which are composition relationships. As I am going to draw a composition relationship line from B to A and C to A, does this mean I cannot also include the data members within the class A "box" because the relationship is inferred from the composition relationship lines?

I ask because the data member variable names seem a good way to help understand the context and this cannot be represented if you omit the data members from the class A "box"??

I am not sure if there is a cast-iron rule in UML or whether I am free to choose. This is not for auto-generation of code- just human reading.

Answer 1

At least, in UML you can show a name of each property like a figure below.