Generate human readable operating period phrases (de: Erzeugung leicht verständlicher Verkehrstageformulierungen)

There are multiple kinds of information about operating periods available in the railML files:

1. operatingPeriod/@timetablePeriodRef
2. operatingPeriod/@bitMask
3. operatingPeriod/@startDate and operatingPeriod/@endDate
4. operatingDay/@operatingCode
5. operatingDay/@operatingCode and operatingDay/@startDate and operatingDay/@endDate
6. operatingDayDeviance/@operatingCode and operatingDayDeviance/@holidayOffset
7. operatingDayDeviance/@operatingCode and operatingDayDeviance/@holidayOffset and operatingDayDeviance/@ranking
8. specialService/@type and specialService/@singleDate
9. specialService/@type and specialService/@startDate and specialService/@endDate

What to do with this amount of information? A nice human readable phrase may be deduced, but nevertheless it will possibly not fulfill everyones expectations.

Maybe it can be reduced with railML3 without restricting the possible operating periods.

What to do with specialService/@startTime and specialService/@endTime in operating periods? What is the use case described in railML-Ticket 31 (http://trac.railml.org/ticket/31)?

Why is operatingPeriod/@dayOffset explained at the railML Wiki (http://wiki.railml.org/index.php?title=TT:operatingPeriod) but not implemented - means meanwhile deleted (http://trac.railml.org/ticket/138).

See also #9 (closed) for the basic behaviour