The German national library released its authority records as linked data.
News and reference services have content management systems that don’t use URIs, so how do they link up public linked data with their private data?
In a way that they can share the resulting linked data within their organization?
Exploration question: What mapping facilities exist in popular CMS systems for mapping linked data to local data?
I don’t know the answer to that but will be finding out.
In the meantime, if you know your CMS system cannot do such a mapping, consider using topic maps. (topicmaps.org)
Topic maps can create linked data that is not subject to the limitation of using URIs.