While reviewing some transformed records at BIBFRAME.org, I noticed that class-LCC is a URI, but class-DDC is a text string.  FWIW, DDC is available as linked data – see http://dewey.info  – in the event anyone wants to include DDC URIs in their transformations. 

Caveat -- A friend at DDC warned that while not all DDC numbers are retrievable to their full build out, the service will return a URI to the closest retrievable number in the hierarchy.

-Nancy