Remove the DataLink class, which is now replaced with the prov:Location class.
Remove the InputPort class and OutputPort class, and consolidate them into a single Port class to simplify the model.  Rely on the semantics of the hasInPort and hasOutPort properties when determining the role of an instance of a Port.
Add the Author class, and distinguish between the Author role (Workflow/Program specification) and the User role (Workflow/Program execution).