[Tagging] Thoughts on how to replace or modify an exist/established tag (Was: Feature Proposal - RFC - sluice_gate)

Peter Wendorff wendorff at uni-paderborn.de
Thu Jan 6 22:15:26 GMT 2011

Hi Simone.
I agree that some definition of "core features" would be useful.
I think I wrote that in my last mail here, too.

I simply don't see the benefit of a certificate on application side.

Let's consider two alternatives.
Either the certification requires support for the most 5 important 
attributes A,B,C,D,E.
An application decides to support A,B,C,D,E,F - and gets the certificate.
Another application decides to support A,B,D,E,F,G and his call for a 
cert is rejected because of the missing C.

But: Is that really an indicator for bad quality? Or - on the other way 
around: is it a sign for quality to follow the suggestions of the here 
defining part of the OSM-Community about a subset of tags?

What's the goal of these certificates? Advertising possibility for the 
application? "this printed map of Las Vegas supports core 1.1, cycle 
1.34, foot 4.12 and boat4.4"? Add as much "features" to the feature list 
as not applicable to the used bbox to get more plus points?


Am 06.01.2011 22:03, schrieb Simone Saviolo:
> 2011/1/6 Ralf Kleineisel <ralf at kleineisel.de <mailto:ralf at kleineisel.de>>
>     On 01/06/2011 06:00 PM, Peter Wendorff wrote:
>     > What beside of this - I fear, stupid - "certification" is the
>     benefit
>     > for a hiking map in supporting e.g. maxspeed of motorways as
>     part of the
>     > OSM core being the decision basis to get the certification?
>     >
>     > To make a better example: Garmin AiO for Europe is getting too
>     large for
>     > many devices currently - so the core definition you propose would
>     > require to include buildings in the map, no matter of their size
>     and the
>     > drawbacks of excluding most old devices by including the
>     building layer?
>     I think it's even impossible to support all OSM tags on a specific
>     map.
>     When rendering a map or converting the data into a special format
>     (e.g.
>     Garmin devices) you always have lot of constraints.
>     For example Garmins don't support an unlimited number of way types. So
>     you have to map OSM tags to device tags, which is not always a
>     lossless
>     process.
>     In addition it's often not even desirable to show everything -
>     many maps
>     have a special purpose and should only show the things relevant
>     for that
>     purpose.
>     I think that map renderers and map makers already do their best to
>     support as many useful (for their map!) tags as possible and most
>     mappers do their best to map according to the wiki definition because
>     they want their work to appear on the maps.
> Yes, and I think of this "certification" (it may not be the best name 
> for it) as a way to indicate that a certain application supports all 
> the map features from a set that has been considered essential.
> To reply to Peter, I would think of a "core" set of features 
> (including main geographic features like coastlines, rivers or country 
> boundaries, and a minimal set of other features, such as highway=* or 
> place=*) that should be included in any map; on top of that, other 
> more specific features would be in a specialized set, for example 
> "Cycle Map Features" including the main tags related to cycleways. 
> Thus, a map for cyclists that has both the Core and the Cycle Map 
> Features should be considered at least a decent map - in that it 
> correctly handles the information that is useful for its intended 
> users. A map for boat navigation of a lake would of course not need 
> the Cycle Map Features "certification".
>     Remember, the goal of OSM is a FREE map, not one with a lot of
>     rules and
>     restrictions. There are enough restricted maps out there.
> Sure, but it's a matter of defining a line between "chaos" and 
> "coordinated anarchy". It seems that many OSMers would not want to go 
> any further than an anarchy, this may be ok, but for the data to be 
> somehow useful (and not only a bunch of self-referential, 
> self-glorifying material) coordination is needed.
> We need to know that oneway=-1 is either "ok" or "not ok", so that 
> consumers know whether they should handle it or not. If you lean on 
> the side of supporting anything you see in the database more than X 
> times, then you get very complicated (and costly!) consumers; if you 
> lean on the side of using only what's documented in the wiki, you risk 
> leaving out a lot because some mapper in his basement decided that to 
> him it's ethical to use oneway=-1 rather than reverting the way's 
> orientation.
> This step is needed if we ever want to do something serious with the 
> data. I visited a few places these holidays, and wanted to check the 
> map there for errors or updates. To make a very simple example, I 
> found several roundabouts not tagged with junction=roundabout. Some 
> were circular ways with oneway=yes (some had oneway=true), some had 
> area=yes on them, some had the importance of the most important 
> incident road, others didn't. Now, in this case it was easy for me to 
> fix them, because roundabouts have a well-agreed tagging scheme, but 
> if the feature had been one of those for which there's controversy, 
> what should I have done? I couldn't have done any QA, because "if the 
> mapper marked that like this, then I should probably respect his 
> decision" - otherwise I may start an edit war.Or was it a poor edit, 
> maybe by a newbie, that never got fixed - how would I know?
> We're at the point where local groups of mappers map the same thing 
> their own "regional" way, because Germans are for x=y while Italians 
> think x=z is better, and Italians from Lombardy are fans of x=z2, but 
> Americans think the feature is not even relevant enough to be mapped. 
> There's never going to be any useful map larger than a few hundred 
> kilometres this way, except for a few "mature" features.
> I hope this opinion doesn't get flamed as "anti-wiki". I'm all for 
> wikis, but a minimum of control is needed. When Wikiversity was 
> created, I suggested that some users with proven credentials be put in 
> charge of their own matter: for example, that one or more doctors in 
> Civil Engineering took care of the Civil Engineering course. I was 
> told that that's not how a wiki works and that a "wiki"versity should 
> be open to anybody's edits - I left the project because then the 
> Wikipedia effect is always latent: anyone could put any garbage in it 
> and it may go unnoticed. I wonder how long it would be before someone 
> noticed if I added a fictional city somewhere. Maybe there are no 
> mappers in the area and the city would stay. So people would load the 
> map in their GPS and be guided through it, only to find rice fields 
> where they should go.
> In other words: if we ever want a map created from OSM data to be used 
> in anything bigger than a proof of concept, or if we - practically - 
> wish to see hand-held devices with an OSM map on them someday, then we 
> definitely need *at least* to be able to do QA, and this can only be 
> done if there's a set of rules. Of course these rules should only 
> cover a mature subset of the current tags! But at least those should 
> have such a thing.
> Best regards,
> Simone
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> Tagging at openstreetmap.org
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