The integration layer will have to deal with two different viewpoints:

• Organization IT system and business process viewpoint: An organization business process may be hosted in an ERP such as SAP. In such a situation, when a specific business event warrants the invocation of a smart contract, this may be issued through a Business API (BAPI) call from the SAP system. The API call from the ERP may contain a variety of data structures, some of which will be completely irrelevant to the blockchain network.
• Smart contract viewpoint: This viewpoint has the particularity of having a data representation that is application agnostic. This means that all participants of the network will understand the nature of the data being processed.

It is up to the integration layer to reconcile the two and ensure that the proper semantic of the transaction is maintained in both systems. This may imply:

• Mapping: Moving data from one field name to the another
• Transformation: Aggregating, splitting, or computing a new value based on input
• Cross-referencing: Leveraging a reference table to map application-specific codes to values recognized by the network

The point here is that even if your network agrees to use the Hyperledger Composer REST gateway presented in Chapter 7, A Business Network Example, there is still work that needs to be done by each participant to ensure that the integration fits into the overall business processes of the organization.