SIRI-VM Subscription Request Topic Info: VehicleMonitoringRef

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MGGomes

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Sep 27, 2021, 8:03:05 AM9/27/21
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Hello everyone!

Help needed from any of you SIRI gurus out there.

Context: SIRI Vehicle Monitoring Subscrition Request, Topic information

Problem: I'm strugggling to really understand what VehicleMonitoringRef really means...
Everything is clear about VehicleRef, LineRef or DirectionRef (pre-defined reference information as per the Operator/Authority).
In one way or the other they are present in some of the other subscription requests.
These are just fine.

As per VehicleMonitoringRef, it is documented in the xsd as being "A predefined scope for making VEHICLE requests.".
What does this mean? A predefined group of vehicles? A predefined group of vehicles on some given line(s) travelling to some given direction?
What's the scope's scope, so to speak? 

Adding insult to injury, one of the examples given surprisingly adds a <DestinationRef> element to the topic info.

(...)
<!--=======TOPIC ===================================== -->
<VehicleMonitoringRef>VIS123</VehicleMonitoringRef>
<DestinationRef>Place875</DestinationRef>
<VehicleMonitoringDetailLevel>minimum</VehicleMonitoringDetailLevel>
(...)

Where does this <DestinationRef> come from?
Unless I'm mistaken (it happens more often than I'd like to admit...) It is NOT included in the xsd file, in the VehicleMonitoringTopicGroup.

To end with a smaller issue: according to the xsd I believe it is possible to send a VehicleMonitoringSubscriptionRequest with no topic information whatsoever (meaning: do not filter the results, give me everything you have!).
Am I correct, here?

I'd be really grateful if someone could shed some light on this.

Thanks!

All the best,

Miguel

Sean Barbeau

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Sep 28, 2021, 9:36:33 AM9/28/21
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Miguel,
I'd suggest taking a look at MTA NYC's Bus Time API documentation, which explains how they are using SIRI VehicleMonitoring:

tl;dr - the scope is defined by the parameters you send to the server - it can be one, some, or all vehicles. So if you include <VehicleRef>, you'll get information about just that vehicle ID. If you include just <OperatorRef>, it will be for all vehicles for that operator.

I'm not sure on <DestinationRef> - is that maybe corresponding to headsign? I don't believe MTA NYC supports this.

And yes, I believe if you don't provide any of the optional parameters, you'll get a dump of all operating vehicles.

Sean

Sean Barbeau
Center for Urban Transportation Research
University of South Florida

Miguel Gentil Gomes

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Sep 29, 2021, 11:10:53 AM9/29/21
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Thanks, Sean!

I'll definitely take a look at that information.

Best regards,

Miguel

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