a resource such as a Subscription that is used to support a stateful pattern of interaction must have certain characteristics, such as an endpoint reference, with which Consumer and Notification Producer can agree to refer to the resource, and an address to which notification message can be sent

NOTE 1 to entry WS-PubSub indicates what these characteristics and equivalent elements are present in SIRI: note however that for some SIRI implementations, some resource properties may be specified statically in the configuration, rather than being specified dynamically on each individual message.

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.

a system that participates in the exchange of messages using the SIRI protocols

NOTE A Participant has a Participant Reference, used to identify the participant in message exchanges, and also used to provide a general purpose namespace to scope arbitrary identifiers of model elements such as line and vehicle identifiers. In SIRI Consumers and Notification Producers (i.e. Control Centres) are Participants.

an entity that receives Notification messages from a Producer as a result of a previous Subscription made to a Service

NOTE In SIRI, in order to manage recovery, a Consumer must know the Subscriber which asked for its subscriptions.

a SIRI Notification Producer mediates the flow of notifications it processes so as to reduce the amount of data traffic to a subscriber. All SIRI subscriptions for a Subscriber are automatically assigned to a Subscriber Channel. The subscriptions in a channel are mediated collectively; if a Situation affects more than one subscription within a channel, only a single notification is sent to the subscriber. The resulting delivery contains all updates for all subscriptions in the channel. There is at least one subscriber channel per Subscriber; some implementations may allow more than one channel for a given subscriber.

a Subscription Manager is a service that allows a Service requestor to create and manipulate Subscription Resources. A Subscription Manager is subordinate to the Notification Producer and may be implemented by the Notification Producer service, or separately as desired. In SIRI only limited capabilities to manage subscriptions are provided.

a message from the Subscriber client to the Notification Producer to create a Subscription

NOTE In SIRI a Subscription Request contains one or more SIRI Functional Service Subscription Requests.

a Delivery from the Server to the Client, returned in response to a Subscription Request; either confirming the creation or other change to a Subscription, or giving an Error Condition

the allowed duration of a Subscription

NOTE In SIRI, leases are specified by an Initial Termination Time and cannot be negotiated or renewed.

the identifier issued to identify an individual request within a conversation, and subsequently used to refer to the request in further exchanges within a stateful resource pattern, such as Publish/Subscribe, or Fetched Delivery

a message or message sequence sent from the Producer to the Consumer to return payload content, either in immediate response to a Request, or sent asynchronously when a Notification Producer determines that the conditions of a Subscription are satisfied

a two step Delivery in which first a Data Ready message is sent from the Producer service to the Consumer to notify the Consumer that data is ready, and then secondly the Consumer fetches the data by sending a Data Supply request to the Producer Service, which then finally sends a Data Supply Response message with the actual payload

an entity that processes events in the data feeds and sends Notification messages to a Producer for brokering and distribution to Consumers

NOTE The Producer may carry out additional mediation such as filtering or data transformation. The use of a Notification Producer is transparent in SIRI.

the act of transmitting a Notification Message to a Notification Consumer. Notifications are sent from the Publisher to the Producer and then from the Producer to the Consumer. The direct unmediated forwarding of notifications from the Publisher by the Producer without filtering or transformation is termed ‘unbrokered’ notification. SIRI requires the mediation of messages by the Producer.

a Client that receives Notification Messages from a Notification Producer

NOTE The role may be performed by the same or a different entity as that of the Subscriber who created the Subscription which requested the sending of the Notification Messages in the first place.

a concept used by a Notification Producer to categorise Notification Messages to decide which Subscribers should be sent a Notification

NOTE 1 to entry A Subscriber specifies which Topics it is interested in as part of its Subscription Request.