Thread:Extension talk:MultimediaViewer/Retrieving Metadata from locally uploaded files/reply (5)

CommonsMetadata follows the prescriptions of commons:COM:MRD very strictly: tables have to be tables, s have to be s, ids have to be ids and not classes. That was probably not a good idea, but that's how it is.

If you just want to test whether your system works at all, you can grab the information template from the export, that one is guranateed to work.