Found this project very interesting:
The Underlay is a global, distributed graph of public knowledge. Initial hosts will include universities and individuals, such that no single group controls the content. This is an attempt to replicate the richness of private knowledge graphs in a public, decentralized manner.
It looks quite relevant to the Solid goals: with the availability of the open public knowledge graph, any Solid app should be able to query the open data using tools like SPARQL. I think it opens quite interesting possibilities and options for all kinds of apps.
However, there’s no information whether the knowledge graph will use RDF and Linked Data or not, so I contacted the authors of the projects and asked some questions about the design and implementation – will update here once I get a reply.