Components as Complex Elements in Software Components
Components can be used as complex elements within software components. Whereas basic elements are defined in the software component they are contained in, complex elements are included by reference, i.e. if the included component is changed, those changes are effective within the including software component. You can connect other diagram items to the inputs and outputs of the included component.
See also
Including a Component as a Complex Element
Layout of Included Components (block diagrams only)