It's not clear to me that GraphQL and Datalog solve the same problems. GraphQL, to me, is fundamentally about designing the interface between a client and server, decoupled from the logic that satisfies requests. I think it's actually not a query language at all, any more than HTTP is a query language. Datalog is very much a query engine. And it's not super clear to me that the services exposed by a server map cleanly to a logic model. GraphQL requires no such purity.