oh the idea is that [G] has type=route, but no route=* because it may be
used in any form of route (with some 'common sense' of course); route
does not apply until [C] so route=road would not get reused. there is
actually a small error, [D/E] is the same and stays exclusively within
public transport. unless you actively map an island I would hope you are
joking. in case you weren't the context is that someone made a whole
fake settlement on an actual island so it would render on the main page
and someone had to revert a whole load of changesets. I can't imagine
much friction from the local community if I make an example relation
alongside the current one and add a note that until further notice
although based on real data it's a proof of concept though. I'll reply
to my own email and add a slightly more updated version (just of the
example) addressing some of this, just to make sure it's clear what I
meant. if you feel an example would help somewhat I'll make one too; it
could be useful to see how renderers handle it now. let me know if you'd
like a 'physical' example.
On 3/15/19 3:00 PM, Jo wrote:
Good analysis Seirra,
I would not "reuse" route=road in other route=* relations though.
route=bicycle might share segments with route=foot/walking/hiking, but
I'd keep everything related to bus/trolley_bus and coach together in
terms of sharing of subroutes not mix it with other route types.
For public transport the biggest benefit will be ease of maintenance.
The way I see it route=bus relation should describe a single variation
in itinerary, and thus include all the stops for that variation. So in
my view the subroutes only contain ways.
I would create subroutes for each direction of travel, so no
forward/backward roles need to become involved. If the subroute would
only contain a single way, a subroute relation probably wasn't needed.
Paul Allen, I did read your objections to this, but that bus route is
wildly exceptional, whereas buses travelling along 'corridors',
reusing the same roads as the rest of the lines is very common (as
that is where the stops are, obviously).
Maybe I should try to create an example somewhere. Preferably a small
island....
Polyglot
On Fri, Mar 15, 2019 at 3:38 PM seirra blake
<sophietheopos...@yandex.com <mailto:sophietheopos...@yandex.com>> wrote:
I can see *a lot* of shared routes in my area because most of the
buses heavily use a star topography (everything must take you to a
central station) as opposed to a hybrid mesh/star topography
(everywhere has access to a service to a central station, but
there are circular routes to allow quicker travel in some
circumstances). for example my local service has one incredibly
early train station detour (presumably for long distance
commuters), the two main routes (incoming/outgoing) and a route
that stops at the bus depot. all 4 of these routes share a large
part of it and that's just one route number! such route segments
could help shrink and simplify maintaining the relations a lot.
for example if there's a detour due to roadworks, you don't have
to edit the very large number of relations individually, (our bus
station has around 20 bays, each taking multiple services...) just
the shared child relations. I don't think we need a specially
labelled super route relation, but perhaps we do need a way to
tell the data user that a segment is shared. these are the
problems I see:
1. where do the tags go?
2. do you need a separate one for each direction?
3. is type=super_route or similar the best idea?
4. how far can they nest?
5. a shared route is being used for public transport, should the
stop positions and bus stops be included with all the ways?
so... what do we do? this is what I see as a solution:
1. if a route is shared, tags should be minimal and only related
to the physical route itself perhaps not even including the
usual route tag (AFAIK wouldn't just about any route relation
in existence define the route tag? so this would just be
another pointer to the software that this isn't your regular
route. but maybe it still is best to tag it, in which case....
maybe route=shared?), rather than things such as what bus
routes it is part or anything, this can easily be seen simply
by looking at parent relations
2. maybe use the roles forward/backward? I don't think these are
used for much any more
3. what do we gain? I think this can more easily be solved by
simply adding another tag such as shared=yes which can tell
the software that there are route relations that are intended
to be treated as just one big way. see below for a more
detailed explanation.
4. I don't see a reason to limit the nesting, I imagine in most
use cases, the benefit of sharing duplicate relation data
probably outweighs any impact from processing nesting
5. if a shared route is used for both a numbered road route and
public transport it's probably unfair on the road user that
doesn't need them if they are included. also this would make
it difficult to work out where to place it in a public
transport V2 relation.. as they have stops at the top, ways at
the bottom but this has both!
so here's an indented, somewhat simplified example of how it
roughly would nest based on the idea of a public transport route,
a cycle route and a road relation that share the same set of ways
(_underlined_=can be shared in parent nesting level, *bold*=can be
shared in nesting levels outside of the parent one, italic=the
level at which main tagging should occur. for easier referencing
each equivalent level of nesting has been assigned a letter):
_______________________________________________________________________________
/bus network///[A]/
/
/route_master=bus /[B]
/route variant/ [C]
_*route segments*_ [D]
_combined bus stop/way relation suitable for
public transport v2_ [E]
_shared bus stop relation_ [F]_
_
_*shared way relation*_ [G]
/road network///[A]/
/
/road /[C]
_*shared way relation*_ [G]*
*
/cycle network//**/[A]/*
*/
/cycle route /[C]
__
__
*_shared way relation_* [G]
_____________________________________________________________________________
potential new tags that may be required:
[C]: shared=yes (defaults to no)
[E/F/G]: route=shared (this is questionable in terms of benefits
though)
_____________________________________________________________________________
notes:
[G] may be infinitely nested as required to prevent duplicate sets
of ways (although this should rarely be required)
as you can see, this allows a lot of the data to be shared between
the various types of relations, whilst also allowing current
relation structure to remain the same, this is just an extra
higher level of detail, where required. due to the way public
transport relations are handled it may be required to even have
every segment in [D] contained in a relation, however as cycle and
road relations are purely made up of ways they may not need the
same kind of treatment and be able to mix items from [G] with
directly referenced ways. the separation of bus stop and way data
allows public transport relations to still correctly identify the
different bus stops in each direction but not have to duplicate
the way data. the naming of parts is solved, as this can be
applied to [G] level relations. the use of [G] and [C] would help
solve where routes need to be split up to keep maintenance
possible. [E], [F] and [G] theoretically shouldn't need to be
tagged as the fact they include any child relations at all should
be enough to indicate what they are, however if not route=shared
would certainly make it obvious. I hope this theory on how we
could solve it was helpful, if any further clarification is
required or there's a notable mistake/error please let me know and
I'll try to respond as best as I can to that. I have thought about
perhaps making an example of this, if it would help please let me
know.
**
On 3/15/19 12:07 PM, marc marc wrote:
Le 15.03.19 à 12:27, Hufkratzer a écrit :
is that a good/sufficient reason to define a new relation type?
imho nearly no routing tools (nor foot nor bus) is currently able
to use a relation type=route with relations as child.
so that's a good reason to create/improve a doc if superrelation is
needed for ex for routing (of course maybe some mapper need superroute
only for the fun of having a relation that collect all other).
for ex how a "data user" can detect "it 's a superroute" <> "it's 2
route with a shared segment" ?
for the moment, the trick is to notice that the name of the main
relationship is close to the name of the children's relationships
and to know that the names of all these children's relationships
are fake names (which should therefore be removed/corrected).
there is for ex nothing called "European long distance path E4 - part
France". it's an artificial name to descript how the relation is splited
maybe the tag network should be the same and/or the name (the country
XYZ may move the a scope tag)
the main relation must/should/mustn't/shouldn't have all/some same tag
as the child ?
all/a lot of child tag must move to the main relation only ? (that's
what we do with MP : we don't duplicate alls tags to way + relation)
etc...
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