What is a CorDapp?

CorDapps (Corda Distributed Applications) are distributed applications that run on the Corda platform. The goal of a CorDapp is to allow nodes to reach agreement on updates to the ledger. They achieve this goal by defining flows that Corda node owners can invoke through RPC calls:

node diagram CorDapps are made up of the following key components:

  • States, defining the facts over which agreement is reached (see Key Concepts - States)
  • Contracts, defining what constitutes a valid ledger update (see Key Concepts - Contracts)
  • Services, providing long-lived utilities within the node
  • Serialisation whitelists, restricting what types your node will receive off the wire

Each CorDapp is installed at the level of the individual node, rather than on the network itself. For example, a node owner may choose to install the Bond Trading CorDapp, with the following components:

  • A BondState, used to represent bonds as shared facts on the ledger

  • A BondContract, used to govern which ledger updates involving BondState states are valid

  • Three flows:>

    • An IssueBondFlow, allowing new BondState states to be issued onto the ledger
    • A TradeBondFlow, allowing existing BondState states to be bought and sold on the ledger
    • An ExitBondFlow, allowing existing BondState states to be exited from the ledger

After installing this CorDapp, the node owner will be able to use the flows defined by the CorDapp to agree ledger updates related to issuance, sale, purchase and exit of bonds.