I'm not sure either what exactly this is, but it reminds me of https://blockstack.org/ when it comes to each user owning their own data storage which the app runs on.
Blockstack essentially lets you pick for example Dropbox as the datastore and an app would save files in a directory on your Dropbox instead of a server controlled by the app developer.
Solid seems to talk about also keeping track of your social connections. So I suppose it also tracks people's profile data and public keys locally?
I heard a funny story once about an interaction between Tim Berners-Lee and Ryan Shea. Woulda been about 4 years ago and I can see how it might have prompted TBL to take a crack at the same problem. Maybe you're right?
Blockstack essentially lets you pick for example Dropbox as the datastore and an app would save files in a directory on your Dropbox instead of a server controlled by the app developer.
Solid seems to talk about also keeping track of your social connections. So I suppose it also tracks people's profile data and public keys locally?