Element for train grouping
Some special timetable phenomenon are trains with the same train number but different operating periods or different routes. They are currently modelled as parallel <train>
elements with the same trainNumber and additional scope attributes.
These trains may be grouped together using typical XML technologies - a so called "container element". I suggest to define something like the following:
<trainGroup trainNumber="a12345">
<train scope="primary" additionalNumber="1" .../>
<train scope="secondaryStart" additionalNumber="2" .../>
...
</trainGroup>
It is as 'nice to have' enhancement for better understanding.
The idea comes from Simon Heller.