Thanks for the hint!

I looked at this one, but I don't just want to reference, I want the metadata to *live* on nostr. Currently some teacher publishes a learning resource somewhere at attached some metadata like subject, taught competencies, appropriate educational level and so on. And then this data is fixed. In current infrastructure approaches it is not easy to adjust this metadata. Maybe it was published with subject biology, but you want to add chemistry as well and add some description on how you used it in chemistry.
Nostr is like made for this. People can fork the metadata and add their suitable Infos to it. The resource stays the same though referenced by the uri where it currently lives.
If you then think of WoT facilities you could provide a user lots of relevant services like when they search for content you can sort results based on their social graph and take into account with what resources (or their metadata) users already interacted with and so on.