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

Steve Bennett stevagewp at gmail.com
Thu Jan 6 04:07:48 GMT 2011

  On 6/01/2011 2:00 PM, John Smith wrote:
> This seems to be an area that OSM *really* lacks, and some people give
> usage of tags as a reason not to improve things which doesn't seem
> like a valid argument especially when some tags like abutters and
> created_by have been depreciated.
> I'm spit balling here, but maybe one way to achieve might be to do the
> following:
> 1) Make a proposal and post to the tagging list asking for feedback/discussion
> Wait a week or two after the last post and then:
> 2) Post to the talk list asking for feedback/discussion
> 3) About 2 weeks after the last discussion/modifications to the
> proposal you post a vote request to both the tagging and the talk
> lists
> Depending on the outcome of the vote, either too many against at which
> point you could try modifying the proposal and going back to steps 2
> or 3, or if the vote is successful or if there was a lack of interest
> in the outcome you could jump to step 4
> 4) Update the wiki to reflect the outcome
4a) Update Potlatch 2's stylesheets and presets to reflect the outcome
4b) Update JOSM to reflect the outcome
4c) Update Mapnik's stylesheets to reflect the outcome
4d) Update Osmosis's stylesheets to reflect the outcome
4e) Update Mkgmap (err, whatever it's called) to reflect the outcome.
4f) Assist external editors, renderers and other tools to reflect the 
outcome (Cloudmade, Mapquest, Nearmap, iPhone apps...)
> 5) Use the XAPI to find existing tags and mass retag using your JOSM
> or any other editor that can handle OSM XML files.
My guess is that this mailing list and talk@ reach a pretty small 
proportion of users. Simply announcing "we're changing the tag! please 
tag differently from now on!" is not remotely sufficient.

Similarly, doing a mass tag update which is going to break many existing 
renderers and editors is simply not acceptable. Particularly when some 
of these seem to update very slowly. We can't have thousands of entities 
suddenly disappearing off the main mapnik view until, some weeks or 
months later, someone gets around to updating the stylesheets.

Putting in place a serious process for tag migration will be difficult. 
I suggest that a first step will be definition of an actual schema, with 
version number. For example, define an actual list of several hundred 
tags, with semantics, that correspond to "OSM core 1.0". Then, we could 
have votes on changes to the schema, with advance notice given: "On 
November 1, 2011, the main database will be updated to OSM core 1.1. 
Please have your editor and renderer patches ready for this date."

Not easy, and I don't think the OSM community is at that level of 
process maturity yet.


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