A Commercial Part is related to 1 or more Vendor Parts.
Ofcourse you can assign all kind of Datasets to any object, but it doesn't make sence to assign a CAD Dataset to the PartItem. In your example you use Structure Manager. There you can combine all Object Types.
First you need to be sure how your datamodel looks like. (ObjectTypes, Relations etc)
You can check the following blog for more info about Part and Design Objects.