Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Paul Norman]

On 1/29/2016 8:49 AM, Matthijs Melissen wrote:

On 29 January 2016 at 17:37, Mateusz Konieczny  wrote:

"but that's not much to do with tagging diversity" - I would dispute
it, from my personal experience. Tagging diversity IS one of real
problems in using OSM data.

+1.


I'm going to disagree, even though I understand exactly why both Mateusz 
and Matthijs come to this conclusion. As an OpenStreetMap Carto 
maintainer, tag fragmentation is a pain. For most data consumers? It 
doesn't matter. Most of the time they're using a small number of well 
established tags, and if they run into an edge case where there's tag 
fragmentation they're not going put in a great deal of time.


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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Richard Fairhurst]

Mateusz Konieczny wrote:
> I am not claiming that there are quick & easy ways to reduce 
> complexity - but complexity has some real negative consequences.

The cycleway tagging mess has come about because a bunch of wikifiddlers
keep inventing ever more spurious and unnecessary tags - highway=path,
bicycle=designated, bicycle=official, and so on. That's an argument to
distrust the wiki, not to give it more authority.

If we were to elevate the wiki to 'MUST' status, you'd have to support a new
set of tags every time ten people voted on one obscure wiki page. At least,
with the current situation, any tag needs to get some sort of critical mass
before clients need to worry about supporting it.

FWIW, I process cycleways extensively for cycle.travel's map and routing,
covering Western Europe and North America. The variant tags aren't great but
they're not that much of a problem - nothing that a few ifs and tables can't
solve (Lua ftw). The three serious problems I do encounter are:

1. Granular tags (notoriously highway=path) with missing information.
highway=path without both access= and surface= tags is pretty much useless.
2. Differing densities of data, such as Germany with its countless
highway=tracks - makes effective cartography from a single stylesheet very
difficult.
3. Bad imported data, principally but not exclusively TIGER.

Richard



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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Roland Olbricht]

  > "but that's not much to do with tagging diversity" - I would
  > dispute it, from my personal experience. Tagging diversity IS one
  > of real problems in using OSM data.

Could you please give an example?


My first ever attempt to display cycleways

[...]

Thank you very much. Now I understand the problem.

There should be for a relatively clear concept like cycleways a 
relatively easy-to-find tagging. Bonus points if the wiki does tell that 
tagging.


I think the problem is that cycleway infrastructure on the ground is 
quite diverse. There are ways allowed for cyclists only, ways that are 
dedicated to cyclists and all kinds of combinations with other modes of 
traffic where bicycles are accepted. I've even seen paved tram tracks 
where bicycles are allowed.


Because individual cyclists will disagree on which particular kind of 
ways are acceptable or preferred, it will be difficult to improve the 
situation much.


Maybe it would be best to work on the well-kept wiki page
http://wiki.osm.org/wiki/Bicycle
to include the missing cases.

Cheers,

Roland


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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Matthijs Melissen]

On 29 January 2016 at 17:37, Mateusz Konieczny  wrote:
> "but that's not much to do with tagging diversity" - I would dispute
> it, from my personal experience. Tagging diversity IS one of real
> problems in using OSM data.

+1.

-- Matthijs

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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Mateusz Konieczny]

On Thu, 28 Jan 2016 19:50:11 +
Andy Townsend  wrote:

> On 28/01/2016 19:16, David Marchal wrote:
> > Hello, there.
> >
> > On a GitHub issue 
> > (https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685),
> >  
> > I've been told that Wiki tagging votes are only advisory and that
> > the community is only invited, neither required nor recommended, to
> > follow them. As I understand this comment, the community MAY follow
> > the Wiki tagging or votes, it does not SHOULD nor MUST follow them.
> > I was under the impression that the community at least SHOULD apply
> > the votes results, MUST looking unenforceable due to the free
> > tagging principle. Am I wrong on that? What is the applicability of
> > the Wiki content?
> >
> 
> What are you going to do when a new mapper comes along and adds a tag 
> that they "SHOULD NOT"?  They won't have read the wiki, because
> no-one* does.  Are you going to send the wiki police around and tell
> them to delete the offending tag with no other sudden movements? :-)

In most cases - this tag will not be rendered/processed/accepted by
data consumers and hopefully mapper will notice that something is wrong
and investigate.

In many cases it will happen in editor itself - for example
natural=tree in JOSM will result in a nice icon, natural=treee will not,

At least some editors (like JOSM) have validator that will complain.

> More seriously, any dataset that has no rules enforced at the API
> level must be assumed to have data in it that doesn't meet a
> specification that is written down somewhere, but not enforced.

OSM database will always have some minor amount of complete junk
([surface=paved;unpaved] or [surface=paved; paved; unpaved; unpaved] or
[surface=paved; unpaved; unpaved; unpaved; unpaved; unpaved; unpaved;
unpaved; paved; unpaved; paved; unpaved; unpaved; unpaved; paved;
paved; paved] - see
http://taginfo.openstreetmap.org//search?q=surface%3Dpaved%3Bunpaved ).

That is not a major problem, and this thread is about another
topic - whatever results of discussion/voting on wiki should have impact
on editing software, map styles and editors (the same arguments may be
applied to discussion on tagging mailing list).

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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Roland Olbricht]

>> This diversity of tagging is often quoted as a problem for data
>> consumers. Oddly, this is often by people who don't actually use the
>> data but feel it must be awkward. Actually it's not. All OSM data has
>> to processed before use. This processing can be fairly
>> straightforward or really complex, but that's not much to do with
>> tagging diversity. Whatever the processing is (LUA code, SQL code or
>> any other coding) it only has to written once and can be used over
>> and over again.
>
> "but that's not much to do with tagging diversity" - I would dispute
> it, from my personal experience. Tagging diversity IS one of real
> problems in using OSM data.

Could you please give an example?

I would like to the contrary to give you two examples where free-form 
tagging helps:


Once you start to do routing for various variants wheel devices for 
people (wheelchairs, walking frames, stroller, trolleys and probably 
more, let's say roller skates) you realize that there are wild 
differences how sensitive they react to various kinds of obstacles. It's 
not only low or high curbs. It's also about width, incline, steps with 
or without ramps, surface, and again probably more. The precise limit 
may depend on wheel size, capabilities of the user to lift, tilt, rotate 
or carry the device, physical strength.


When you start to use the data then the places where your model fails 
are precisely the places where you learn most how to improve your data 
model. The used tags and even more the expected but missing tags will 
tell a lot about the story what you safely can assume, can reasonably 
guess or where you better ought err on the safe side.


If you ask people to misrepresent the reality to fit a fixed tagging 
scheme then you have to find those places in a haystack of bent or not 
bent data. Precisely: your end users will find those places the hard way.


The second example is even more clear-cut:

In most countries, a bus stop is legally defined by the corresponding 
traffic sign. If there is no sign then there is no bus stop. If and only 
if you wait at the sign then the bus driver will stop to let you board, 
hand waving may be required. A straightforward model would be to set a 
node where to sign stands.


However, the wiki got distracted over bikeshedding around the relatively 
unimportant question whether to call it "highway=bus_stop" or something 
with "public_transport". That's a single line of code to for a data 
consumer to handle both. Nobody cared about the various places where 
information about public transport is stored. The result is that the 
wiki suggests on various pages all mixtures of using a platform, using a 
sometimes fictional node on the way, using the traffic sign or any 
combination of it. I've even found bus stops where a well-meaning mapper 
has replaced the traffic sign node by a fictional node on the street, 
i.e. converted precise on-the-ground verifiable information to an 
imprecise, non verifiable information.


There is a clear-cut legal definition and the vocal amongst the wiki 
users got it wrong. Hence, now every mapper has to decide with his tool 
of choice how to least misrepresent the local reality.


However, if one tries to get through the various wiki pages to clean up 
things then one still finds a lot of partisan resistance against turning 
it to the legal definition - it's not worth the time to fight through.


The mechanism at work is: To get a wiki majority, you need a lot of time 
and a dedication to write personal messages. To map properly or to make 
a faithful data consumer you must be able to make precise observations 
and to know enough similar places and acknowledge their slight 
differences. There are few or no people that can and appreciate both.


Hence, it doesn't make much sense to take the wiki too serious. Looking 
at taginfo will tell you which and how many tags have to be considered 
to get 80%, 95% or sometimes even 99.9% of all cases right, and looking 
at the remaining places will make obvious what to do next to get even 
further - fixing data or fixing the assumed model.


Cheers,

Roland


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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Mateusz Konieczny]

On Fri, 29 Jan 2016 19:38:46 +0100
Roland Olbricht  wrote:

>  >> This diversity of tagging is often quoted as a problem for data
>  >> consumers. Oddly, this is often by people who don't actually use
>  >> the data but feel it must be awkward. Actually it's not. All OSM
>  >> data has to processed before use. This processing can be fairly
>  >> straightforward or really complex, but that's not much to do with
>  >> tagging diversity. Whatever the processing is (LUA code, SQL code
>  >> or any other coding) it only has to written once and can be used
>  >> over and over again.
>  >
>  > "but that's not much to do with tagging diversity" - I would
>  > dispute it, from my personal experience. Tagging diversity IS one
>  > of real problems in using OSM data.
> 
> Could you please give an example?

My first ever attempt to display cycleways went as follows:

- display ways tagged as highway=cycleway

Why nearly everything is missing? OK, there is also bicycle=designated

- display also bicycle=designated

Failed due to people adding vehicle=designated, bicycle=designated,
horse=designated etc to a normal roads (rare, but enough to result in
noticeable errors)

- replace bicycle=designated by [highway=path; bicycle=designated]

Later I also discovered that [highway=footway; bicycle=designated]
combination also appears (due to
https://github.com/openstreetmap/iD/issues/2327 ).

That would be OK. But it is not going to work properly. There are
still cycleway=track ways. Also, [highway=bridleway +
bicycle=designated]. Some people decided that inventing
bicycle=official makes sense - and to handle it at least
[highway=path; bicycle=official] and [highway=footway;
bicycle=official] and [highway=bridleway; bicycle=official] would be
necessary.

There are more accepted in at least some region methods to map
cycleways and even more rare methods. For example tagging joined
footway + cycleway as [highway=footway; cycleway=lane].

There are many places where my map style would fail, as it
would be unable to interpret local tagging scheme.

Remapping/retagging my city was very significant part of this map
project. In the end about 1/2 of work was adding new data, 1/4 editing
data to fit common tagging schemes and creating transformations to
handle tagging complexity and 1/4 was making map style.

For reference - this project is a horrible mix of Maperitive
and Ruby scripts and at least currently resides at
https://github.com/matkoniecz/bicycle_map_of_Krakow ).


I am not claiming that there are quick & easy ways to reduce complexity
- but complexity has some real negative consequences.

> If you ask people to misrepresent the reality to fit a fixed tagging 
> scheme

That is clearly not OK, nobody advocates misrepresenting reality.

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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Mateusz Konieczny]

On Thu, 28 Jan 2016 20:31:04 +0100
Matthijs Melissen  wrote:

> On 28 January 2016 at 20:16, David Marchal  wrote:
> > On a GitHub issue
> > (https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685),
> > I've been told that Wiki tagging votes are only advisory and that
> > the community is only invited, neither required nor recommended, to
> > follow them. As I understand this comment, the community MAY follow
> > the Wiki tagging or votes, it does not SHOULD nor MUST follow them.
> > I was under the impression that the community at least SHOULD apply
> > the votes results, MUST looking unenforceable due to the free
> > tagging principle. Am I wrong on that? What is the applicability of
> > the Wiki content?
> 
> I don't think this has ever been formally decided.
> 
> Personally I am of the opinion that the editor software, and to a
> lesser extent the main data consumer software such as
> openstreetmap-carto, has way to much power over tagging standards. I
> would be in favour of giving more power to the community, and I think
> editor/data consumer software should be encouraged to follow the
> standards agreed by the community.
> 
> Often the counterargument is given that only a handful of people vote
> on proposals, but I don't think that's a good argument. Everybody
> *can* join in the discussion and the votes if they want to. Apparently
> the people who don't are not interested, or perhaps they trust the
> regular crowd to make decisions for them. Having the power only in the
> hands of the few people that control the major editors and renderers
> is no good idea, in my opinion. I therefore think that we as a
> community should ask that everybody involved SHOULD follow the voting
> results.

Whenever it is possible and reasonable I prefer to follow wiki
recommendations.

Whenever I notice that wiki and what I consider reasonable to mismatch I
am trying to remove this mismatch (either by editing wiki or by
changing my opinion).

Whenever I encounter mismatch between wiki & tagging or software I
attempt to fix it - by creating issues/PRs or editing OSM data or
by changing wiki.

Complaining that wiki is wrong is not useful - it is wiki, change it. In
some cases opinions are divided and wiki should contain description of
that controversy.

Wiki + taginfo are documentation of tagging schemes - and people
refusing/forgetting to document their tagging schemes should not be
surprised that data consumers follow either wiki documentation or
their own ideas.

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[OSM-talk] Applicability of wiki tagging and votes: may, should or must

[David Marchal]

Hello, there.On a GitHub issue 
(https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685),
 I've been told that Wiki tagging votes are only advisory and that the 
community is only invited, neither required nor recommended, to follow them. As 
I understand this comment, the community MAY follow the Wiki tagging or votes, 
it does not SHOULD nor MUST follow them. I was under the impression that the 
community at least SHOULD apply the votes results, MUST looking unenforceable 
due to the free tagging principle. Am I wrong on that? What is the 
applicability of the Wiki content?Hoping my question isn't too trivial,Regards. 
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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Matthijs Melissen]

On 28 January 2016 at 20:16, David Marchal  wrote:
> On a GitHub issue
> (https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685),
> I've been told that Wiki tagging votes are only advisory and that the
> community is only invited, neither required nor recommended, to follow them.
> As I understand this comment, the community MAY follow the Wiki tagging or
> votes, it does not SHOULD nor MUST follow them. I was under the impression
> that the community at least SHOULD apply the votes results, MUST looking
> unenforceable due to the free tagging principle. Am I wrong on that? What is
> the applicability of the Wiki content?

I don't think this has ever been formally decided.

Personally I am of the opinion that the editor software, and to a
lesser extent the main data consumer software such as
openstreetmap-carto, has way to much power over tagging standards. I
would be in favour of giving more power to the community, and I think
editor/data consumer software should be encouraged to follow the
standards agreed by the community.

Often the counterargument is given that only a handful of people vote
on proposals, but I don't think that's a good argument. Everybody
*can* join in the discussion and the votes if they want to. Apparently
the people who don't are not interested, or perhaps they trust the
regular crowd to make decisions for them. Having the power only in the
hands of the few people that control the major editors and renderers
is no good idea, in my opinion. I therefore think that we as a
community should ask that everybody involved SHOULD follow the voting
results.

-- Matthijs

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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Chris Hill]

On 28/01/16 19:16, David Marchal wrote:

Hello, there.

On a GitHub issue 
(https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685), 
I've been told that Wiki tagging votes are only advisory and that the 
community is only invited, neither required nor recommended, to follow 
them. As I understand this comment, the community MAY follow the Wiki 
tagging or votes, it does not SHOULD nor MUST follow them. I was under 
the impression that the community at least SHOULD apply the votes 
results, MUST looking unenforceable due to the free tagging principle. 
Am I wrong on that? What is the applicability of the Wiki content?


Hoping my question isn't too trivial,

I'd say you might be a bit back-to-front. To me, the wiki works best as 
a way to document the tags that get used in OSM, so people can see the 
way tags get used for the object they have in mind. So the wiki doesn't 
fit the 'SHOULD-follow' bill. OSM is a representation of the weird, 
mixed-up, contradictory world as seen by people with a hugely diverse 
way of looking at it. The OSM needs to reflect that, proscriptive wiki 
pages do not reflect that.


The tagging list is a great example of this diversity. Lots of tags get 
discussed there, but very few firm decisions ever come about, simply 
because real-world examples keep throwing up differences, so tagging 
needs to be able to reflect these.


Taginfo is a useful tool for looking at the diversity in OSM. Some 
people look at the the diversity of tagging and see an opportunity to 
harmonise to a single value: x. What TagInfo actually shows is that 
there are many uses of the key and that x is not the only way to use the 
tag, so why should they all be forced to be the same?


This diversity of tagging is often quoted as a problem for data 
consumers. Oddly, this is often by people who don't actually use the 
data but feel it must be awkward. Actually it's not. All OSM data has to 
processed before use. This processing can be fairly straightforward or 
really complex, but that's not much to do with tagging diversity. 
Whatever the processing is (LUA code, SQL code or any other coding) it 
only has to written once and can be used over and over again.


The wiki has its place, but it is certainly not the Oracle which holds 
all the OSM truth.


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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Andy Townsend]

On 28/01/2016 19:16, David Marchal wrote:

Hello, there.

On a GitHub issue 
(https://github.com/gravitystorm/openstreetmap-carto/issues/2027#issuecomment-174443685), 
I've been told that Wiki tagging votes are only advisory and that the 
community is only invited, neither required nor recommended, to follow 
them. As I understand this comment, the community MAY follow the Wiki 
tagging or votes, it does not SHOULD nor MUST follow them. I was under 
the impression that the community at least SHOULD apply the votes 
results, MUST looking unenforceable due to the free tagging principle. 
Am I wrong on that? What is the applicability of the Wiki content?




What are you going to do when a new mapper comes along and adds a tag 
that they "SHOULD NOT"?  They won't have read the wiki, because no-one* 
does.  Are you going to send the wiki police around and tell them to 
delete the offending tag with no other sudden movements? :-)


More seriously, any dataset that has no rules enforced at the API level 
must be assumed to have data in it that doesn't meet a specification 
that is written down somewhere, but not enforced. Someone wrote that 
wiki page long ago but didn't actually do anything else, presumably 
expecting the magic code and project management fairies to look after 
all the other changes that they expected to happen.


Cheers,

Andy (SomeoneElse)


* to a reasonable approximation across all mappers in the project, just 
like "no-one" reads mailing lists or forums.
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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[Richard Fairhurst]

David Marchal wrote:
> What is the applicability of the Wiki content?

Three long-standing principles of OSM:

   1. consensus is important
   2. precedent is important
   3. patches beat "should"

The first means that you can't order the community to do things based on ten
people voting on the wiki. taginfo, major clients, and agreement on these
lists are also valid indicators of consensus, often more so.

The second means that you can't order the community to do things which break
long-established OSM good practice, even if you've voted it through on the
wiki.

The third means that you can't simply get ten votes on the wiki and require
editor or stylesheet authors to change their code or maps. A vote on the
wiki does not mean that these people have to spend hours coding something
for your new relation scheme, nor does it even mean they are obliged to
accept a patch from you if they disagree with it.

So the applicability of the wiki content is to the wiki. But it is one of
several indicators of consensus in the wider project, and it's consensus
that drives the project and tagging in particular.

Richard



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Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or must

[David Marchal]

To: talk@openstreetmap.org
From: ajt1...@gmail.com
Date: Thu, 28 Jan 2016 19:50:11 +
Subject: Re: [OSM-talk] Applicability of wiki tagging and votes: may, should or 
must
More seriously, any dataset that has no rules enforced at the API level must be 
assumed to have data in it that doesn't meet a specification that is written 
down somewhere, but not enforced.  Someone wrote that wiki page long ago but 
didn't actually do anything else, presumably expecting the magic code and 
project management fairies to look after all the other changes that they 
expected to happen.
I know that the free tagging scheme is one of the main strenghts of OSM, and 
I'm aware of its advantages for modelling the real world, which per se contains 
elements that will never fit in a strict tagging scheme. My point is, there are 
multiple references (editors, Wiki, MLs, and, maybe a bit consumers), which 
regularly contradict one another about what they assume to be the "correct" 
tagging; it would be far more coherent to have a single reference, that users 
SHOULD follow whenever possible, which would be the start of each debate, 
transcript its end and the decisi,ons made, and which would centralize tagging 
defs and their modifications. This way, the undocumented tagging could be 
reduced, at least the unnecessary, unnecessarily confusing part, and increase 
the DB usability for consumers, who would be less required to adjust to the 
different, virtually unlimited, existing tagging schemes.
Note: I use SHOULD as defined in the IETF RFCs 
(https://www.ietf.org/rfc/rfc2119.txt), that is: mean that there may exist 
valid reasons in particular circumstances to ignore a particular item, but the 
full implications must be understood and carefully weighed before choosing a 
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