Product : R3, Corda/3.1, All
Feature : Consensus , Algorithms, Architecture
Content Owner:  MLG Blockchain
Summary
Notaries - Pluggable Framework, Validity consensus and Uniqueness consensus
Details
transaction validity and transaction uniqueness.

https://docs.corda.net/key-concepts-consensus.html

Corda uses special Notary Nodes to reach consensus. Notaries are nodes that specifically address double spend attempts.