| Semantic Constraints for Train Section [message #3048] |
Mon, 30 January 2023 08:22  |
David Lichti
Messages: 13
Registered: December 2020
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Junior Member |
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Dear TT-Community,
There currently are two proposals for semantic constraints on operational and commercial train sections, and their relation to itineraries. The goal of these constraints is prohibit overlaps and gaps in the way sections cover their parent variant's itinerary.
Disjoint Sections
Semantic constraints TT:004 and TT:006 are about pairwise overlaps of train sections in their itinerary. The itinerary is defined by the parent train variant. But it may be subdivided into several sections. These sections must not overlap.
I suggest the following wording:
TT:004.
The itinerary sections of an operationalTrainVariant, defined by the operationalTrainSections and their respective ranges, must be pairwise disjoint, except for their respective first and last baseItineraryPoints.
(Replace operational by commercial for commercial train sections.)
Itinerary Coverage
These constraints are complemented by TT:005 and TT:007, which are about the coverage completeness of these sections. While the constraint above prohibits overlaps between sections, the following constraint prohibits gaps in the coverage of the variant's itinerary.
I suggest the following wording:
TT:005.
The first(last) baseItineraryPoint of each operationalTrainSection within an operationalTrainVariant must either be the referenced itinerary's first(last) base point, or coincide with another section's last(first) base point.
(Replace operational by commercial for commercial train sections.)
Best Regards
David Lichti
[Updated on: Mon, 30 January 2023 08:27] Report message to a moderator |
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| Re: Semantic Constraints for Train Section [message #3049 is a reply to message #3048] |
Mon, 06 February 2023 08:44  |
Milan Wölke
Messages: 139
Registered: April 2007
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Senior Member |
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Hi David,
thanks for the suggestions. From my point of view they sound pretty clear. I dont think they could be misunderstood.
Best regards, Milan
Milan Wölke – Timetable scheme coordinator
railML.org (Registry of Associations: VR 5750)
Altplauen 19h; 01187 Dresden; Germany www.railML.org
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| Re: Semantic Constraints for Train Section [message #3053 is a reply to message #3049] |
Wed, 22 February 2023 15:33 |
Milan Wölke
Messages: 139
Registered: April 2007
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Senior Member |
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Hi all,
in another discussion among the timetable developer group, we found that the semantic constraints would need to be restricted to allow for overlapping in certain scenarios. We found that overlapping would need to be allowed for cancellations as well as for on-request trains. This would apply for both, commercial and operational train sections.
The reasoning behind this is that if a section of a variant is cancelled, it should be possible to describe the replacement. That replacement would then overlap with the cancelled section.
Similarly, it should be possible to describe multiple on-request train sections that could be run if requested.
However the developer group also agreed that a semantic constraint would make sense if those exceptions would be made. That would mean, that teh above wording proposals would need to be adapted:
Quote:
The itinerary sections of an operationalTrainVariant, defined by the operationalTrainSections and their respective ranges, that are not cancelled and not marked as onRequest, must be pairwise disjoint, except for their respective first and last baseItineraryPoints.
The second proposed rule, from my point of view, still applies.
Quote:
The first(last) baseItineraryPoint of each operationalTrainSection within an operationalTrainVariant must either be the referenced itinerary's first(last) base point, or coincide with another section's last(first) base point.
What are your thoughts on this. Do you see other scenarios, where these proposed semantic constraints would pose a problem?
Thanks in advance for your contribution.
Best regards, Milan
Milan Wölke – Timetable scheme coordinator
railML.org (Registry of Associations: VR 5750)
Altplauen 19h; 01187 Dresden; Germany www.railML.org
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