| Re: [railML 2] Semantic Constraint at trackBegin and trackEnd [message #3696 is a reply to message #3547] |
Wed, 13 August 2025 18:58  |
Thomas Nygreen
Messages: 103
Registered: March 2008
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Senior Member |
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Dear all,
For as long as @pos has been documented in our Wiki, the documentation has been:
Since 2011: "This is the position on a track relative to its start in the railML file."
Since 2015: "This is the position on a track defined as distance from its start (trackBegin) regardless the "absolute mileage" in absPos."
with the constraint: "greater than or equal to zero, less than or equal to the track's length"
Equally long, the @pos of <trackBegin> has had the constraint annotation "The start of the track is described by a pos value of zero." And similarly for <trackEnd>: "The end of the track is defined by the "real" length of the track as distance from the trackBegin regardless the "absolute mileage" in absPos."
I agree with Milan that an attribute with a fixed value is redundant. But it seems well-documented for a decade and a half, across five releases of railML 2, that @pos in <trackBegin> needs to be zero.
Best regards,
Thomas
Thomas Nygreen – Common Schema Coordinator
railML.org (Registry of Associations: VR 5750)
Altplauen 19h; 01187 Dresden; Germany www.railML.org
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