[Talk-us] Route Relation Tagging, again (was Re: ref tags)

[Phil! Gold]

* Paul Johnson <baloo at ursamundi.org> [2013-06-24 09:11 -0500]:
> network=US:I
> modifier=Future

* James Mast <rickmastfan67 at hotmail.com> [2013-06-25 00:15 -0400]:
> Now, I'm going to initially use the following to tag the "Future"
> segments inside of relations: network=US:I:Future However, somebody else
> suggested this: network=US:I modifier=Future Which do you guys think
> would be the better way to go?

There's been discussion about how to tag the relations for bannered routes
in the past.  My understanding of the list consensus, as I summarize in
this previous email:

  http://gis.19327.n5.nabble.com/Highway-Shield-Rendering-tp5612357p5640994.html

is that "Future Interstate 26" should be tagged as follows:

    network=US:I:Future
    ref=26
    modifier=Future

However, in a Google Hangout last week, Paul indicated a desire to reopen
the discussion on tagging bannered routes, so here we go:

There are basically three options for tagging bannered routes.  I'll use
Future I-26 as an example here, but the principle applies equally to any
other routes.

Option A (network-classification-per-banner):

    network=US:I:Future
    ref=26
    modifier=Future

Option B (banner-in-ref):

    network=US:I
    ref=26 Future
    modifier=Future

Option C (banner-in-modifier):

    network=US:I
    ref=26
    modifier=Future

In my opinion, either option A or option B should be used.  Because a
veriety of people with a variety of OSM experience edit OSM data, I think
it's important to consider how damaged or incomplete data will be treated
by data consumers.

In any of the above cases, a data consumer that only sees or understands
the ref= tag (e.g. something that was written to handle ways and is now
looking at a relation) will not get a complete picture, but also won't get
a wrong impression (thinking that I-26 is US 26 or something similar).
Furthermore, the network/ref tagging has been pretty well established on
the wiki and in general usage for some time now.

If a data consumer only sees or understands the network and ref tags, both
options A and B will give it a complete picture of the route, but option C
will be incorrectly interpreted as the main I-26.  I think that's a pretty
strong argument against option C.  In programming or database design, one
strives to eliminate all duplication, but in a project like OSM I think a
little duplication of data serves as useful redundancy.

Note that if the modifier tag is present, both options A and B can be
processed to remove the redundant information if that's desired.

I think the choice between options A and B is more of an aesthetic one.
What matters is that there is a consensus on what the tagging is.  I think
in previous discussions more people were tipped toward option A because it
makes the decision of when to use a different network easy, because
"network" essentially means "different road sign".  Option B has a little
more grey area, since there were people (well, mostly NE2) saying things
like "alternate and business Interstates are clearly not part of the
Interstate Highway System, but alternate and business US Highways are
clearly part of the US Highway System" (paraphrase from [1] and [2]).

  [1]: http://gis.19327.n5.nabble.com/Highway-Shield-Rendering-tp5612357p5636639.html
  [2]: http://gis.19327.n5.nabble.com/Use-of-ref-tag-on-state-highways-tp5285587p5285594.html

As I said before, my understanding of the list consensus in previous
discussions is for option A and that's what my renderer understands (see
[3]).  If you have an opinion on what we should be using (whether it's one
of options A, B, or C above or some other system), I guess this is the
place to voice that opinion.

  [3]: http://elrond.aperiodic.net/shields/supported.html