Subprocesses help to encapsulate functionality to deal with complexity, enable r

Thank you for your response.
According to the Appian Documentation forum.appian.com/.../Mapping_Subprocess_Data.html
in the "Setup Tab: Input Variables Group Box" section :
"...Each subprocess parameter must hold a system data type. Custom data types cannot be used as parameters of a subprocess..."
Is this true? It would be very restrictive if it is not possible to use CDT as parameters of a sub process. System data types are very primitive abstractions. Talking of Text, Numbers(Integer), Dates...instead of Customer, Order and other business objects does not help to abstract and the business layer does not reveal itself.
Sub processes are useful to encapsulate complexity, but if you cannot pass CDT as parameters, then your sub processes can only pass primitive abstractions as parameters.

Thank you for your response.
According to the Appian Documentation forum.appian.com/.../Mapping_Subprocess_Data.html
in the "Setup Tab: Input Variables Group Box" section :
"...Each subprocess parameter must hold a system data type. Custom data types cannot be used as parameters of a subprocess..."
Is this true? It would be very restrictive if it is not possible to use CDT as parameters of a sub process. System data types are very primitive abstractions. Talking of Text, Numbers(Integer), Dates...instead of Customer, Order and other business objects does not help to abstract and the business layer does not reveal itself.
Sub processes are useful to encapsulate complexity, but if you cannot pass CDT as parameters, then your sub processes can only pass primitive abstractions as parameters.