| Re: To use or not to use? - default values in XSDs [message #1601 is a reply to message #1308] |
Fri, 09 June 2017 11:03  |
Dirk Bräuer
Messages: 311
Registered: August 2008
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Senior Member |
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Dear all,
the matter of default values was again raised during <TT> developer meeting on 1st June 2017 in Berlin. The result from the <TT> developers is:
- In general, default values may be used in railML.
- The default values must not be country-specific.
- Each default value is an individual, isolated case and has to be documented concerning its meaning and function (at least in Wiki). There is no rule such as "default means unknown".
Typical examples for reasonable default values - which do NOT mean "unknown" - are:
- <TT>..<times> @arrivalDay=0 / departureDay=0
- <TT>..<ocpTT> @guaranteedPass=false
A fine example for a context-sensitive default value is:
- <IS>..<speedChange> @trainRelation: =headOfTrain when effectively decreasing, =endOfTrain when effectively increasing permitted speed, whereas increasing/decreasing can possibly only be determined from merging different speed profiles.
With best regards,
Dirk.
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