On 17 Nov 2009, at 12:35, Richard Mann wrote:
On Tue, Nov 17, 2009 at 12:13 PM, Peter Miller <[email protected]
> wrote:
Can I suggest we define some terms.
A Line is all the journeys made using a particular reference (4, X13,
Citi1 etc). Most people actually use the Route relation for this. This
should include all the ways that are travelled on by the vehicle and
all the stops that are called at. It might be helpful to add these
stops in some sort of order (out then back) but it will not always be
possible.
A Line Variant (also know as a Service Variant) is a unique stopping
pattern for a bunch of Journeys within a Line. (ie inbound, outbound,
inbound via the school, outbound but stopping at the station and not
going to the end of the route etc). This would include all the stops
in order. however..... I strongly suggest we don't add this data to
OSM - it is too complex and not needed for mapping and should be kept
in the schedules service.
In particular, lets not start using the term Line to describe only a
single direction (ie a variant) or we will get horribly confused.
I think having the two directions in one relation is a recipe for
confusion, because putting "forward_stop" as a role could refer to
the direction of the bus service or the semi-arbitrary direction of
the way. It's almost bound to be a mess. Whereas it's a lot clearer
if the two directions are in separate relations. The only problem
with splitting the two directions, as far as I can see, is editor
support for having 2 x umpteen relations on a way.
I think you are making a false assumption that a Line only has two
variants. Often they have more than two and sometimes as many as ten.
The only way to establish all the variants is to inspect the schedules
in detail which is why I recommend that we duck the issue and only
include enough information to produce a good bus map.
Regards,
Peter
Richard
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