what value should be given to the TN Document Type field URI

Hi ,

In Centrasite asset TN document type. what is the significance of URI ?
I understand that this is to represent the defined document types in Trading networks.
For example we have a Rosettanet TNdoc type named:PIP3C3 NextGen Generic External Document.
What should be the URI value?

the URI is set automatically on publish from IS/TN and gets populated with the IS namespace value.