A DC can contain other DCs. These DCs then belong exclusively to the enclosing parent DC; outside of the parent DC, they are not visible. This allows you to encapsulate the functions of the child DC. For more information, see Nesting Development Components.
If you want particular public part entities of the child component to be visible outside of the parent component, then the parent component can include a public part entity reference to a public part of the child DC into one of its own public parts.
Any DC that has access to the DC owning this public part can generate a public part entity reference.