M.-T. Schmidt B. Hutchison P. Lambros R. Phippen The Enterprise Service Bus (ESB) is the infrastructure which underpins a fully integrated and flexible end-to-end service-oriented architecture (SOA). This paper details the essential meta-data and capabilities of the ESB. It presents a summary of the key concepts of the ESB and defines the integration model for it, including key user roles. These roles are fulfilled using meta-data that describes the service endpoints, such as the service interface and policy requirements and capabilities. The ESB manages this meta-data through a registry, which supports configuration, connection, matchmaking, and discovery of service endpoints. Some typical mediation patterns that are used to satisfy endpoint policies are explored, and usage patterns are described in which the ESB is used to implement real SOAs.