# Transformation of Inbound Messages

You can configure Substation ES to subscribe to and process requests generated by a TIBCO messaging application, for example, inbound messages.

To configure Substation ES to subscribe to and process requests generated by a TIBCO messaging application, you have to specify the following items:

- The message subject to listen for
- How data is transformed for delivery to a transaction processing application
- The method of invocation (MOI)
- Whether to return data (or some type of reply) to the calling application

If return data or an acknowledgement is expected from the transaction processing application, you must specify how the data or acknowledgement is transformed for the calling application.

For information about messaging flow and different types of MOIs, see TIBCO Substation ES Concepts.

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