© 2004Kizoom

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SIRI - Service Interface for Real Time Information

(CEN-OO278181 ) http://www.siri.org.uk

27- 29 Cursitor StreetLondon, EC4A 1LT

nick_knowles@kizoom.com

Siri 0.1g v3.6b

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Topics

• General Background

• Transport & Communications

• Specific Functional Services

• Review Process and Completion

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General Background& Overview

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SIRI - CEN TC278 WG3 SG7• Real-time Server-to-Server Services for PTVs

– Based on: • TransModel : Terminology, model (isomorphic)• XML, WS-PubSub Web Service enabled• VDV 453,454, Trident, RTIG – Real systems & experience!

– Useful for Specifying & Implementing AVMS, PTI and UTMC systems– European economies of scale

• Participants– Germany (VDV453, VDV 454)– France (Trident , TransModel)– UK (RTIG-XML, TransModel)– Denmark, Sweden, Norway, (PubTrans)

• Deliverables (April 2005)– Technical Standard Document (for consultation)– Supporting XML Schema – W3C .XSD– Support WSDL /SOAP binding using same xsd schema

• Migration path from existing standards

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Gene Pool

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Motivation - Uses Of SIRI Services

• Rapid growth in real-time info - makes PT more efficient & more attractive to use.– Provision of Real time Service Information to

Passengers. • At Stop, On board, tethered & mobile internet

– Provision of Information to Journey Planners. • Real-time augmented

– Facilitating Connections for Passengers. – PT Fleet and Network Management.– General Business Communication.

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Motivation - Standards

• Value to PTEs / Customers– Open architectures & supplier independence.– Protection of investment.– Efficient tender specification criteria.

• Value to Suppliers– European economies of scale & markets.– Reduced complexity & deployment costs

• More reuse, Cheaper integration– Simplified tendering, quality differentiator.

• Value to Both– Enables new types of services– Lowers costs - creating new markets– Modern, Modular, scaleable architectures– Harnesses open internet standards

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Support Different Operation Models

• Interfaces can be used for different operational models

Vehicle tracking and management

Information for

passengers

Bus 1 Bus 2

RTI core data model

Prediction generator

(a) UNITARY single control and information centre

Information for

passengers

Bus 1

Vehicle tracking and management

RTI core data model

Prediction generator

(b) INTEGRATORseparate control and information centres

Bus 2

Vehicle tracking and management

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Support Different Environments

• Able to optimise for different operational characteristics– High/Low bandwidth– Fast/slow processors – Hi/Low traffic– Large/small networks– Sparse /dense usage

• Able to optimise for different operational characteristics

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Technical Challenges

• How to give migration path from existing standards– VDV, RTIG, TRIDENT– Allow alternative delivery patterns– Allow alternative formats for some detailed response messages

where necessary. Semantically identical.– Allow modular, incremental implementation: roadmap

• What is canonical TransModel XML?– Trident XML not being kept current

• Further improvements in TransModel since Trident• New developments/standards in XML / WS technology• Further application requirements for SIRI

• What real-time efficiency optimisations are needed?– Principle of strict Transmodel Isomorphism ?– Allow different message patterns and tradeoffs

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SIRI Approach & Services

• Separation of Concerns– Transport layer is separate (http &/or SOAP)– SIRI General Communications Services

• Common to all types of Functional Service• Robust, scaleable, architecture for Real Time• Tuneable for efficient deployment

– SIRI Functional Services • Timetables & Timetable Changes • Stop Events (Arrivals & Departures) • Vehicle Movement • Connection Protection (Timetables, Events)• General Informative Messages

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SIRI is an XML Dynamic Protocol

• What to Exchange?– Message Payload Structure

• Content model Requests, responses,• Derived from TransModel + National systems

– Data reference systems• Stop identifiers, Lines, times etc

• How to Exchange it?– Protocols & message patterns– Transport– Mediation

• Derived from existing National systems

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Transport & General

Communications

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General Communications Services #1

• Common Protocols for all SIRI Functional Services– Independent of Functional Message Content– Based on new Web services standard Ws-

PubSub, Ws-Address etc (W3C) – Communications Transport Independent

• XML + http POST, • WSDL SOAP Binding

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SIRI Communications Layer

• Common to all Functional Services

SIRI interface

Service 1 –used

Organisation 1or System 1

Organisation 2or System 2

Communications Service Layer – common

Service 2 –not used

Service n –used

Service 3 –not used

)…

sends receives

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General Communications Services #1

• General Functions Common to all SIRI Service Types– Subscription Management– Recovery & Restart– Access Controls – Versioning– Discovery

• Some Capabilities are Optional

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General Communications Services #2

• Alternate Patterns of Interaction1. Request/Response vs. Publish/Subscribe

• Choose for scaleability & responsibility

2. Direct Delivery vs. Fetched Delivery• Allows efficient implementation choices

3. Notification Mediation• Reduces traffic for publish subscribe

– Last Update, Change Threshold,– Subscriber Groups

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Interaction 1- Request/Response

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Interaction 2- Publish/Subscribe

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Publish Subscribe -WS-PubSub • New Coherent Family of web service standards for stateful

patterns of interaction . IBM, Microsoft, Tipco, Akamai, Sonic– State

• WS-Address W3C• WS-BaseFaults• WS-Resource• WS-Topics• WS-ServiceGroup

– Stateful Resource Patterns• WS-Resource Lifetime• WS-BaseNotification • WS-BrokeredNotification• WS-PubSub

• SIRI aims to be WS-PubSub enabled – Similar concepts, terminology and separation of concerns– SIRI V1 does not attempt a SOAP WSDL encoding / binding

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Subscription Management

• Roles “Stateful pattern of interaction”– Subscriber assigns identifier– Notification Producer grants new subscriptions– Subscription manager handles any changes

• Notification Producer & Manager know each other

• Management Messages– SubscriptionRequest

• SubscriptionIdentifier

– SubscriptionResponse• Granted or refused

– TerminateSubscriptionRequest

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Delivery - Direct & Fetched

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Mediation

• Filtering of Data & Notifications to Reduce data traffic– Incremental Data Changes:

• Only send data changes since last update

– Change threshold • Only notify if change is more than a certain amount

– Grouping of subscriptions • One notification for changes to many subscriptions

in a group

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Mediation

• Interaction of simple patterns can be quite complex.

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Use of Interaction PatternsMediation Direct

DeliveryFetched

Delivery

Request / Response

-- RtigXml,

Trident

--

Publish / Subscribe

Last Update RtigXml,

Trident

VDV453

Change Threshold

Subscription Aggregation

--

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SIRI Functional Services

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PT Systems & SIRI Interfaces

a a

Generic model of PT operations, showing exchange points for RTI

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SIRI Timetable Servcies

• Production Timetable– Distribute latest timetable

• Schedule to AVMS• AVMS to client

• Estimated Timeable– Distribute latest timetable including real-time

• Cancellations, additions, short working• Realtime-predictions

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SIRI Stop Services

• Stop Timetable– Distribute latest timetable

• Stop Centric Timetable• Provisions Clients.

• Stop Monitoring– Real time Arrival & Departure Boards – Arrivals, Departures, passthroughs

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SIRI Connection Services

• Connection Timetable– Distribute planned interchanges

• Stop Centric • Provisions Clients.

• Connection Monitoring– Connection management– Guranteed connection support

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SIRI General Message Services

• General Message– Exchange structured messages

• Simple or embedded structures

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SIRI Further Technical Points

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SIRI Data Models • TransModel based; Small Subset • Common Concepts& Elements

– Participants (Systems)– StopPoints (Pluggable to national systems)– Lines, Directions– Journeys,

• VehicleJourneys & Calls• DatedVehicleJourneys & Calls• MonitoredVehcielJourneys & Calls• ConnectingJourneys

– Features• Service• Vehicle• Product

• Common Structures– Isomorphic optimisations of TransModel for use in

interface

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Acceptable Optimisations =TransModel Isomorphic?

A

B

F

C

D

*

*

Bs

Cs

E

G *

1 1

A

X(C+D+E)

* Cs

G

1

1

1

1

*

A

B

C

D

*

*

Bs

Cs

E

G

*

1

1

1

1

OK NOT OK

Compression

Compounding

*

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SIRI Functional Requests

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SIRI Subscription Requests

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SIRI Common Request Structure

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Subscription Response

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Response Status

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Siri Delive

ry

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Common Delivery Structure

• Example Delivery for Stop Monitoring

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Recovery & Restart

• Subscriber is responsible for recreating subscriptions on restart,

• Consumer is responsible for Detecting Loss– Check Status– Heartbeat

• Consumer must know Subscriber!

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Detecting a Loss of Service – Check Status

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Detecting a Loss of Service - Heartbeat

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Extensions

• Access Control– Well defined Capabilities– Request based Checking

• Discovery– Capability– Coverage

• Stops• Lines• Product, Service, Vehicle - Features /Attributes ?

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Access Controls

• Optional Capability on Requests– By ParticipantCode

• Configuration Matrix• Restrict By

– By Function &/or Capability (Static)• E.g. Stop Events, Vehicle Movements

– E.g. Subscribe, detail level – By Topic (Dynamic)

• E.g. Certain Stops, Certain Lines

– By Resource level (Dynamic)

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Discovery

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Stop Points Delivery

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Discovering Capabilities