Hi Michael
In the new proposal I am missing some details on how to build relations:
1. Should the outward and return trip be represented as two separate
relations, as a single relation or is that up to the mapper?
Each direction should be in a separate relation. This is written in the
proposal. Both directions/variants should be member of a master relation.
2. Which members should the relation contain, and in which order?
You are not the first with this question, so I added some explanations
to the proposal:
First the stop_positions ordered (with role stop), then platforms
ordered (with role platform) and then the ways ordered (without role).
3. Which data primitive should be added for stops?
Stop positions AND platform. Stop position is important for the route
itself, the platform is important for pedestrian routing.
4. How are line variants mapped?
Problem 1:
A - B1/B2 - C - D - E1/E2 - F
In morning and evening hours the bus stops at B2 instead of B1.
During school holiday the bus stops at E2 instead of E1.
This gives us four possibilities really used.
When you add alt-roles to a stop you can't say when is what route used.
So this does not work, we need really four relations.
Problem 2:
What do you want to say with role forward/backward? Forward/backward
compared to what? To the route direction or to the tagged way direction?
Actually both is used in the OSM database and no one knows how to
interpret it. Role forward and backward is in my eyes a nice try to
solve a problem. But it confused more then it solved. We should leave
this away.
Practical:
I map the variant with the most stops (in your example twice A B1 E1 K.
In JOSM you can easily copy a relation and change what is different. So
to handle your 8 variants should not take 8 times mapping one variant.
I personally leave away the very special cases (ex. first course starts
at B instead of A). This is only relevant when timetable information is
added to.
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