A system for exchanging transaction messages between different computer systems includes a data processor for monitoring transaction messages. The data processor has a transaction processor for assigning identifiers to both inbound transaction messages from source executable applications and outbound transaction messages for communication to destination executable applications, to individually identify transaction messages. The data processor has a repository of map information associating inbound and outbound transaction messages using the assigned identifiers and a user interface for providing data representing at least one display image and including data identifying an inbound or outbound transaction message and a corresponding outbound or inbound transaction message, in response to a user command.