DNG 6/7: reporting on non-delivered Change Sets?
Accepted answer
Undelivered changesets in a stream are exposed in DN as a small supported extension of the CM API - although in 7.0.2 there was a defect which made all changesets visible this is resolved in one of the recent iFixes so just make sure you use the most recent (currently iFix014). I guess you'll have to write a script to get to these because they aren't put into the TRS for LQE - the API will return all undelivered changesets for a stream. See how to discover the configs in a component in my answer here (search for 'to details of all the configurations in the component' https://jazz.net/forum/questions/266334/dng-oslcfetch-components-from-project-area/266667 - although note the RDF there doesn't show undelivered changesets only because there weren't any in the stream I used as the example.
One other answer
Looking at examples of DOORS Next service provider catalogs (/rm/oslc_rm/catalog and /rm/oslc_config) I do not see any OSLC query capabilities for configurations or change sets. So there doesn't appear to be any OSLC defined way of querying for change sets.
I would highly recommend that you only use public APIs. The public APIs are documented at https://jazz.net/wiki/bin/view/Deployment/CLMProductAPILanding. Private APIs are typically not documented, not supported for customer or 3rd party use, and may change without notice between releases. Implementations using them may find their use case are fragile over time, and not supportable.