[Tagging] Superroutes - good, bad or ugly?

seirra blake sophietheopossum at yandex.com
Fri Mar 15 19:13:12 UTC 2019

I can understand your concern. I did actually consider mentioning 
something about skipping stops.. but I forgot to, I spent a good few 
hours on the original, so I guess my thoughts got easily distracted. 
I'll make an example based on the real data to help illustrate the idea, 
but I'll also include an imaginary express version that only stops at a 
few major stops. provided everything goes as planned I'll link to a 
fairly realistic example in version 4 (I need version 3 to fix a mistake 
I made). I understand that you may not want to follow each version due 
to being busy or whatever, so until the example is ready any future 
version will be 3.x (so for example: 3.0,3.1,3.2...); this way you'll be 
able to Ctrl+f and search for '#4', if there's no #4 it isn't ready yet 
and so you won't waste your time reading through the changelog for it. 
as for seeing all the stops/being able to compare to official feeds, 
that may fall more under what the renderer is expected to do, as it 
should already be reading all the segments as one whole route.

On 3/15/19 6:30 PM, Jo wrote:
> When I start mapping a bus line, I have several route relations which 
> contain all the stops for each variation in itinerary.
> When I add the ways, it would be nice to reuse subroute relations for 
> the parts where ways are shared between lines.
> When I come back later and I want to compare whether the number of 
> variations for a line is still the same, I want to compare against 
> sequences of stops in the route relations, hence the reason why I 
> would not add the stops to the subroute segments. (Compare against 
> data from the operator or GTFS)
> We also have 'express' lines that skip stops. if the stops are put in 
> the subroute relations, then they can not be reused for those lines.
> As far as I'm concerned, the sequence of stops is the 'signature' 
> defining each variation in itinerary.
> Polyglot
> On Fri, Mar 15, 2019 at 6:55 PM seirra blake 
> <sophietheopossum at yandex.com <mailto:sophietheopossum at yandex.com>> wrote:
>     key: almost tagging should occur here | data may be reused in
>     parent | data may be reused in parent and any 'adjacent' (with the
>     same letter) parent
>     /public transport network///[A]/
>     /
>         /route_master=public transport /[B]
>             /route variant/ [C]
>                 _combined stop/way relation suitable for public
>                 transport v2_ [E]
>                     _*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 (to tell the software there is use of shared ways,
>     but the software probably should be able to work that out)
>     [E/F/G]: route=shared (this is considered in case type=route
>     explicitly requires a route=* key)
>     _____________________________________________________________________________
>     notes:
>       * [G] may be infinitely nested as required to prevent duplicate
>         sets of ways (although this should rarely be required)
>       * [G] may require names in some cases and should always require
>         type=route, but should include no other tags unless it very
>         specifically relates to only the members of the relation and
>         can't be included in any parent relation (unicorns are
>         probably more common)
>       * [G] should almost always not be used for a single way unless
>         it will assist in maintainability. if a
>       * I don't believe route_master=public transport actually exists,
>         but the same concept should work for any public transport
>       * the route=* tag should not be required until you move up to
>         [C], shared way relations and bus stop relations should be
>         open to any route type to increase re-usability
>       * as they are just a connected line of ways, shared way
>         relations should be usable in either direction, the direction
>         to use could be specified via a role. although reusable for
>         routes going in the same direction, [E] will rarely be
>         reusable for both directions of a route because it contains
>         both platforms and stops, and platforms usually differ
>         depending on direction.
>       * if this becomes accepted it may become a good idea to specify
>         a members limit for relations (at which point it should be
>         split up). such ways should probably
>       * I may consider adding a rough idea on perceived pros/cons,
>         depending on demand
>       * I may add a more visual version, depending on demand
>       * I may add an actual example, depending on demand (if you wish
>         to add your own as well, or an inspired version please base it
>         heavily on reality if it is on main OSM. do not make any
>         existing route relations unusable)
>     _____________________________________________________________________________
>     changelog:
>     #0
>       * initial concept
>     #1
>       * removed [D] and [F]. [D] was meant to be removed prior to
>         sending, [F] is not required.
>       * added a few more notes so it may be referred to on its own
>       * the bus example applies to any public transport really, adjust
>         language accordingly
>       * warned against damaging existing relations' usability/the
>         creation of fictional data
>       * added extra details on a request if needed basis
>       * added this changelog and relevant versioning to help people
>         keep track. this should be traceable to the (unlabelled) version 0
>     special thanks:
>       * you may request your name here and optionally credits for
>         ideas you contributed (being kept in an opt in basis in case
>         people don't want their names shown)
>     On 3/15/19 2:37 PM, seirra blake 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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