These API specifications use the terminology used throughout the rest of the Technical Documents for consistency. In practice, the API when coded would use ISO 20022 terminology for consistency with the final payment instruction.
Term used in these documents
ISO 20022 Term
Source Liquidity Provider
Intermediary Agent 1
This is not defined separately in ISO20022, instead will take the place as Debtor or Creditor in the local IPS instruction (and the Debtor or Creditor is moved to Ultimate Debtor or Creditor)