UML aggregation. Is necessary to put an atributte? -

I am creating a UML class diagram and I do not know how to do this:

Nearly there is a content in which the file is both content and file are displayed in the form of classes. I have kept the aggregation between the content and the file but I do not know that for the representation of the file, it is necessary to put a contribution inside the content or not. what is required?

Thank you.

You can create composition in two ways:

2. You can combine two classes with a union and add a name for it

In your case you have a group There is no reason to add the field after making (which is a type of union).