The present invention, known as the Middleware Brokering System Adapter, is a component useful with a Middleware Brokering System, which brokers messages between middleware computing products. Each middleware service can send data to and receive data from the Middleware Brokering System in its native data format and programming syntax. The Middleware Brokering System Adapter is a component of the Middleware Brokering System that transforms data messages from the native format of a middleware computing product or a mainframe computing system into a format known as a structured event and from a structured event into the native format of the middleware product or the mainframe system. In an embodiment of the invention, the Middleware Brokering System Adapter maps the fields of a Cobol copybook onto the fields of a structured event and the fields of a structured event onto the fields of a copybook. In an alternative embodiment, the Middleware Brokering System Adapter maps the fields of a Java Messaging Service MapMessage onto the fields of a structured event and the fields of a structured event onto the fields of a MapMessage.