| Re: Semantic Constraints for Train Section [message #3053 is a reply to message #3049] |
Wed, 22 February 2023 15:33   |
Milan Wölke
Messages: 141
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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