Documents are messages that travel over a network from a publisher to a subscriber, through the Broker. The role of the Broker is to route documents between information producers (publishers) and information consumers (subscribers). The Broker receives, queues, and delivers documents.

Each document is an instance of a document type. A document type is a schema-like definition that describes the structure of a document that publishers and subscribers can exchange using the Broker. A document type has a unique name, a structure that consists of named fields, and a set of properties that determines how the Broker handles instances of that document type at run time. Clients indicate which documents they want to receive by subscribing to specific document types.