Home » railML newsgroups » railml.timetable » Formation versus TrainParts (Differences between modelling combinations of portion working)
Formation versus TrainParts [message #2326] Wed, 12 February 2020 17:08 Go to next message
Stefan de Konink is currently offline  Stefan de Konink
Messages: 5
Registered: August 2019
Junior Member
We are currently implementing an open source converter from NeTEx (the European CEN standard for the exchange of network and timetables) and RailML 2.4. While having produced XSD-valid railML 2.4 files, the (new) software supplier of our launching customer complains about the way we have modeled portion working.

The ground truth is being exported from Giro Hastus is CEN NeTEx. We are in control of the (open source) OIG script used for this step. In order to model portion working we are using NeTEx VehicleServices to differentate between tasks a vehicle has to operate. A task begins and ends at a depot, making it analogue to a NeTEx Block. For each task we know the NeTEx VehicleType. To improve our data quality for the traveler perspective we integrate VehicleTypes into the more specific NeTEx CompoundTrain which is virtually analogue to a RailML formation.
Our source data does not split vehicles within a single commercial trip.

In our implementation we differentiate between formations for sections that trains run coupled. An example would be a long train splitting into two short trains. Each formation has been assigned an individual RailML Block matching a NeTEx VehicleService. Where the RailML Block references to RailML blockPart which are shared between blocks. This allows us to create 1:1 relationship between a blockPart, trainPart and train having an unambiguous RailML train, including a formation. Important detail: we are not duplicating trainParts or trains, each train has a single trainPart, always having a single formation.

The new software vendor insists on a different model: every subsection of the long train should be a unique and duplicated (so not just referenced to a trainPartRef as in TT_Rostering.xml example) down to the lowest common
formation. Trains would be consisting of trainParts with a short_a and short_b formation. The fact that short_a and short_b is formation_long, is lost.

Main modelling differences:


  • our model has three blocks, referencing to 1 single blockpart, referencing 1 single trainPart. "This is per block what should be executed"
  • their model creates two rosterings (long, short). Long is operated shared, short individually. Having in total three blocks, referencing to unique blockParts, referencing to unique trainParts (duplicating the timetable). "This is per train/trip what it consists of"
Given that both of our models (except for their private attribute) match the XSD validator, and our model can loaded into railVIVID without errors. Can we expect that our producer interface could be certificated as-is? If our method is not compliant with the scheme RailML proposes, could anyone state why grouping by formation is a bad practice?
Re: Formation versus TrainParts [message #2377 is a reply to message #2326] Mon, 09 March 2020 12:47 Go to previous message
Dirk Bräuer is currently offline  Dirk Bräuer
Messages: 311
Registered: August 2008
Senior Member
Dear Stefan,

I hope I understand your problem right.

Which vehicles should be grouped into formations and which into several block[Parts] of circulations depends on the use case and is not defined by railML.

The general intention behind is:
- What operates separately, should be an own formation and have an own block in a circulation.
- What always operates coupled, should be grouped in the same formation and circulation block.

If you have two Multiple Units which operate coupled most of the time, but operate separated even only one single trip, they are should be separated into different formations, trainParts and blocks.

If you have a Rail Car consisting of a driven motor unit and a non-driven driving trailer, which naturally operate always together (between two overhaul periods at least), they should share the same formations, trainParts and blocks.

However, this is no strict rule. This rather refers to the traditional practice of timetabling and not to strict software practice.

For instance it would also be possible to define a formation, consisting of a locomotive and several coaches, including a dining car:
<formation id='fmt_1'>
<trainOrder>
<vehicleRef orderNumber='1' vehicleRef='veh_Engine' vehicleCount='1'/>
<vehicleRef orderNumber='2' vehicleRef='veh_A' vehicleCount='2'/>
<vehicleRef orderNumber='3' vehicleRef='veh_WR' vehicleCount='1'/>
<vehicleRef orderNumber='4' vehicleRef='veh_B' vehicleCount='6'/>
</trainOrder>
</formation>
whereas veh_A are first-class coaches, veh_B are second-class coaches and veh_WR is the dining car.

This is one <formation>, used by <train>s which have only one <trainPart> consisting of that one <formation>. But, there may be a <rostering> element with the attribute @vehicleRef="veh_WR" and referencing the <trainPart>s (by @trainPartRef) with the full formation:

<rostering id='rost_1' ... vehicleRef='veh_WR' ...>
...
</rostering>

therefore "picking" only one vehicle out of the whole formation. This rather "wild" usage is currently not forbidden by railML. But, it may be forbidden by a certain use case.

I am afraid the problem can only be harmonised by defining special use cases for one or the other solution. It is up to you to suggest such a use case based on the current solution needed by your customers.

Best regards,
Dirk.
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