I read the Eth Yellow Book back then. The opening sentence "A single column state machine with shared state" (shared state machine) was so abstract that it was shocking. The abstraction of computational models is really good. Later, I found out that the author of the Yellow Book was @ gavofwork. Later on, although there were many issues with @ polkadot, it was still being built. The latest technological upgrade called JAM still inherits a better abstraction upgrade for decentralized world computers. But this time the technical document is called a grey book. Let me introduce JAM when I have time.