Every event contains envelope fields and data fields. Envelope fields are consistent for all event types and contain details about the event's sender, destination, and its transit. Envelope fields are described on Envelope Fields.

Event data fields contain the data that your client applications use to exchange information. Event data fields can contain a single value, a sequence of values with the same type, or a structure containing values of different types, or a pre-defined Event Type. Event data fields are discussed on Event Data Fields.