Who is a validating peer?

Question

I don't see a definition of the terms Validating Peer and Non-Validating Peer in the Glossary. It is important to have this definition as a good deal of literature seems to depend on these types of peers.

Coming to my main question.

Looking at the Blockchain as a data-store, it is clear that, this datastore will expose functions to change and read the state of its store. Therefore, is the validating peer an entity that will verify the fact that, X was before state, T was the transaction applied and X' the resulting state?

Or, will the validating peer also verify the business logic that T represents and the access level that should exist to invoke T?

A centralized analogy is an RDBMS that uses a SQL engine to expose the state of store. This store can be updated via a combination of business logic (e.g. a rules engine) and SQL commands (e.g. INSERT, SELECT, etc.) My question is, is a validator interested in ensuring the SQL command worked successfully? Or, does it extend the validation to the rules engine also?

Answer 1

The endorser validates the transaction and sends the RWsets along with the Endorsed signature to the proposal. The proposal then sends the transaction request to the orderer, who chunks the transaction into blocks and passes the blocks to committer peers.

Answer 2

The term validating peer was used in the v0.6 of Hyperledger Fabric. They were the orderers, and the No-validating peers, the Peers.

In the v1.0 there are:

• Endorser Peers: they receive a transaction. Then, they execute the transaction against the Smart Contrat and they sign the result. They send the transaction signed to the peer that has sent it.
• Committer Peers: the Peers get the Blocks (with the validates transactions) and commit them to its ledger.
• Orderes: nodes that sort the transactions and generate the blocks.

Edit (adding the following):

A peer can be Endorser and Comitter. Also, a Endorser Peer can execute its own transactions.

The flow (briefly):

• A peer gets the client request. This peer (the initial Peer) sends to the Endorser Peers the corresponding request.
• The Endorser Peers execute the request against their Smart Contract. They sign the response and send it to the initial Peer.
• If the result of all the responses is equal and the signatures are correct, the initial Peer builds the transaction with the signs. It is sent to de orderer.
• In the Ordering Service the signatures are verified. The Ordering Service creates the blocks cronologically and by channel. They are sent to the Comitter Peers.
• Each Comitter Peer validates each transaction of the Block. If OK, it append the Block to each local ledger.