a web service endpoint is a referenceable, entity, or processor resource to which Web Service messages can be targeted. Endpoint references convey the information needed to identify and reference a Web service.

Endpoint references are used to provide addresses for individual messages sent to and from Web Services, both synchronously and asynchronously. An endpoint reference includes an Address (the URI to which to send a message) and also Endpoint Reference Properties, that identify stateful resources, such as subscriptions. They may also indicate a Port and Processing Policies. WS-PubSub and the other web service standards require the separation of the endpoint references from their bindings to a given transport protocol, such as SOAP.

In SIRI, each Participant is an endpoint for each of its roles in message exchange, i.e. Subscriber, Producer and Consumer. A Subscription Reference is an Endpoint property and is typically made up of two parts: (i) a Participant Reference, which may be specified in the configuration to indicate the Control Centre, and is not necessarily repeated explicitly on individual messages, and (ii) the Subscription Identifier, which is a serial number for an individual subscription that is unique within the SIRI Functional Service and Participant Reference.