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Re: [railML2] trackRef@sequence [message #2162 is a reply to message #2161] Wed, 27 March 2019 13:20 Go to previous messageGo to previous message
Torben Brand is currently offline  Torben Brand
Messages: 158
Registered: March 2016
Senior Member
UChristian Rahmig <coord(at)infrastructurerailmlorg> wrote:
> Dear Torben,
>
> your question adresses the order of track references in an OCP.
>
> Am 05.03.2019 um 10:48 schrieb Torben Brand:
>> Does anyone use trackRef@sequence?
>> https://wiki.railml.org/index.php?title=IS:trackRef_propEqui pment
>>
>> We have a use case where we plan to have a macro model with
>> only the main track forming the network. To indicate the
>> track numbers in ocps we add topology unconnected tracks.
>> The tracks are all connected to the <ocp> through
>> crossSection@ocpRef and listed in
>> ocp/propEquipment/trackRef@ref. Now it would be useful to be
>> able to indicate the order of the parallel tracks in
>> relation to each other. I thought of using trackRef@sequence
>> here. But the wiki definition is to vague for this use case
>> of ordering the tracks:
>>
>> If no sequence is provided, the sequence of the referenced
>> tracks shall be assumed as "arbitrary" or "undefined". In no
>> case the sequence of the XML elements in the XML file shall
>> matter. Either all or none of the <trackRef> elements in the current
>> <propEquipment> element shall carry sequence attributes. The referenced
>> track with the lowest sequence value is
>> interpreted as the first element of the current
>> <propEquipment>. Each sequence value shall only be used once within the
>> current <propEquipment>.
>>
>> I suggest to add the definition to the wiki of
>> trackRef@sequence:
>> "For parallel tracks the order is from right to left as seen
>> in track direction of the main track from lowest to highest
>> @sequence value."
>>
>> Illustration:
>>
>>       |--track@type="secondary" @name="4" --- sequence:3
>> --->
>> |--------track@type="main" @name="2" ---------- sequence:2
>> ---------------------->
>>       |--track@type="secondary" @name="1" --- sequence:1
>> --->
>
> I agree with you that we should extend the description in the wiki in
> order to make better use of the sequence attribute.
>
> What does the community think about Torben's proposal?
>
> I have an alternative suggestion for the order of tracks:
> We could also define an order starting always from the operational
> center of the OCP, e.g. the side where the station building is standing
> (in case there is a station building). This means, that the track
> sequence number increases the farer the track is away from the OCP
> center. Tbd: how about OCP where there are tracks on both sides of the
> center point?
>
> The advantage of this alternative solution is that it does not depend on
> the orientation of the main track. Imagine the situation that there are
> two main tracks (one for each direction) are going through the OCP and
> they are oriented in different directions. How to solve this with your
> approach, Torben?
>
> Best regards
> Christian
>

Hi Christian,
Good to see you are much better!
Thank you again for your valuable critical thinking.
Your approach is much closer to reality. In fact this is the track number
rule in norway for single track lines.

But your suggestion would require that the new attribute
crossSection@ocpCenterSide is set. This is not always the case.

For your suggestion with starting the sequence at the ocp (or main track
for that manner) and with tracks on both sides of the operational center of
the ocp we would need negative numbers for the other side of the reference.
Unfortunately the attribute is of type xs:positiveInteger. We alternative
could group the sequence to their relative position to the reference (ocp
or main reference track). For instance:
- 0-99 left of the reference on line with the operational center of the ocp
or crossSection of the reference main track
- 100-199 right of the reference on line with the operational center of the
ocp or crossSection of the reference main track
- 200-299 left of the reference in front of operational center of the ocp
or crossSection of the reference main track
- 300-399 right of the reference in front of operational center of the ocp
or crossSection of the reference main track
- 400-499 right of the reference behind operational center of the ocp or
crossSection of the reference main track
- 500-599 right of the reference behind operational center of the ocp or
crossSection of the reference main track

With this we also could map shunting tracks the are in the ocp and in the
same relative position as the secondary tracks but but with a higher
kilometration.

As the ocp has no direction, how do you define the left/right side of the
ocp? Here you need to either use track direction or maybe increasing
mileage direction. I would prefer track direction.

For the problem you described in my suggestion (when multiple main tracks
are present) we could introduce the sub rule to if multiple tracks if type
“main” are present in an ocp. use the main track with lowest track number
as the reference for the track sequence.

We could have a hybrid rule:
1. Use ocp (operational center/building) as reference for sequence order.
2. If no crossSection@ocpCenterSide is set use main track as reference.
3. If multiple main tracks are present, use main track with lowest track
number.

Ps. This is my first forum answer within the Newstap app. I hope it looks
ok.
--
TOBR

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