Hi Arne, et. al.
I think the greatest benefit right now, in practical terms, is increasing the discoverability through search and through the current category and linking structured between Wikidata and Wikipedia (for example, interwiki language links on the left-hand side of Wikipedia pages are increasingly including Commons Categories from Wikidata). We don't have a huge amount of evidence, that these things support access (and would welcome any examples folks want to share, like Jos -- or if they have a tactic for examining this data).
In the long term, the greatest benefit will be ease of migration to Structured Data on Commons -- which has lots of discovery and arbitrary query potential. Recently, I wrote a couple recommendations for Martin Poulter, which, if done with GLAM collections now, I am imagining will help a migration to Structured Data on Commons:
- Including as many descriptive metadata templates as you can in existing Commons infoboxes (Institution templates, creator templates, technique templates (basically every type of sub-template type listable at https://commons.wikimedia.org/wiki/Template:Artwork ). These are mapped almost 1-to-1 by a few folks on Commons, so should be fairly easy to migrate long term.
- Ensuring that Commons categories are mapped one-to-one with how Wikidata concepts are being used (depicts, vs topics related to an object), and doing it on Wikidata with Property:P373 property.
- If items are described in Wikidata, adding as many fields as possible.
The Structured data on Commons team is still being assembled, and will be doing research that builds on some initial research from the Wikidata team before doing community consultations around design next-steps:
https://commons.wikimedia.org/wiki/File:HeavyCommonsUserQualitativeResearch.pdf . I am not sure what the final shape of the project's impacts will be/look like, but the more metadata that is consistently displayed now, the easier it will be for the community or institution to take advantage of the benefits of structured Commons later (such as easing attribution and embedding of the mediafile in other sources, surfacing media files in multilingual search, etc).
Cheers,
Alex Stinson