BS DD CEN/TS 15531-2-2007 公共运输.与公共运输操作相关的实时信息服务接口.通信基础设施

标准号：BS DD CEN/TS 15531-2-2007
中文标准名称：公共运输.与公共运输操作相关的实时信息服务接口.通信基础设施
英文标准名称：Public transport - Service interface for real-time information relating to public transport operations - Communications infrastructure
标准类型：R07
发布日期：2007/7/31 12:00:00
实施日期：2007/7/31 12:00:00
中国标准分类号：R07
国际标准分类号：35.240.60
引用标准：CEN/TS 15531-1-2007;ISO/IEC 8859-15;ISO/FDIS 24531
适用范围：SIRI uses a consistent set of general communication protocols to exchange information between client andserver. The same pattern of message exchange may be used to implement different specific functionalinterfaces as sets of concrete message content types.Two well-known specific patterns of client server interaction are used for data exchange in SIRI:Request/Response and Publish/Subscribe.• Request/Response allows for the ad hoc exchange of data on demand from the client.• Publish/Subscribe allows for the repeated asynchronous push of notifications and data to distribute eventsand Situations detected by a Real-time Service.The use of the Publish/Subscribe pattern of interaction follows that described in the Publish-SubscribeNotification for Web Services (WS-PubSub) specification, and as far as possible, SIRI uses the sameseparation of concerns and common terminology for publish/subscribe concepts and interfaces as used inWS-PubSub. WS-PubSub breaks down the server part of the Publish/Subscribe pattern into a number ofseparate named roles and interfaces (for example, Subscriber, Publisher, Notification Producer, andNotification Consumer): in an actual SIRI implementation, certain of these distinct interfaces may be combinedand provided by a single entity. Although SIRI is not currently implemented as a full WS-PubSub web service,the use of a WS-PubSub architecture makes this straightforward to do in future.For the delivery of data in responses (to both requests and subscriptions), SIRI supports two commonpatterns of message exchange, as realised in existent national systems:• A one step ‘Direct Delivery’, as per the classic client-server paradigm, and normal WS-PubSub publishsubscribe usage; and;• A two step ‘Fetched Delivery’ which elaborates the delivery of messages into a sequence of successivemessages pairs to first notify the client, and then to send the data when the client is ready. FetchedDelivery is a stateful pattern in its own right.Each delivery pattern allows different trade-offs for implementation efficiency to be made as appropriate fordifferent target environments.A SIRI implementation may support either or both delivery methods; in order to make the most efficient use ofthe available computational and communication resources. The delivery method may either be preconfiguredand static for a given implementation, or each request or subscription may indicate the delivery methodrequired by the client dynamically as part of the request policy, and the server may refuse a request if it doesnot support that method, giving an appropriate error code.The Interaction patterns and the Delivery patterns are independent aspects of the SIRI protocol and may beused in any combination in different implementations.For a given SIRI Functional Service type (Connection Monitoring, Stop Monitoring etc), the message payloadcontent is the same regardless of whether information is exchanged with a Request/Response orPublish/Subscribe pattern, or whether it is returned by Direct or Fetched Delivery.The SIRI Publish/Subscribe Protocol prescribes particular mediation behaviour for reducing the number ofnotifications and the amount of network traffic arising from subscriptions.The mediation groups the various subscriptions from a subscriber into one or more Subscriber Channels, andis able to manage notifications and updates for the aggregate.Only partial updates to the data set since the last delivery for the subscription need be sent.The SIRI Communication protocols are designed to fail gracefully. Considerations for resilience and recoveryare covered below.