[Tagging] The endless debate about "landcover" as a top-level tag

Paul Allen pla16021 at gmail.com
Sat Jun 9 13:53:34 UTC 2018

On Thu, Jun 7, 2018 at 11:11 PM, Andy Townsend <ajt1047 at gmail.com> wrote:

> On 07/06/18 23:00, Peter Elderson wrote:
>> I think landuse=forest should remain intact, for cases where forestry is
>> actually how the land is used.
>> So the tag is not deprecated, it's just applicated more consistently.
> So you're proposing to change the meaning of a tag that has 3.5 million
> uses?
> I'm sure that you have only the best of intentions, but, er, good luck
> with that :)

Indeed.  Others have pointed out elsewhere that the only way to make this
sort of thing work is with new
tags, such as happened with landuse=farm.  Landuse=farm was ambiguous in
meaning, and the meaning
was unclear in the wiki.  It has been superseded with landuse=farmyard and
landuse=farmland, which cover
the two cases which were formerly dealt with by landuse=farm.

It is also clear (to me) that we should strive to create keys which have
unambiguous meanings in British
English (since that is the dialect used by OSM).  Landuse=forest could mean
a group of trees which are not
consistently used by a single organization for anything (and often called
"Xyz Forest" or "Pqr Wood"), or it
could mean an area used for forestry (and might currently have stumps,
saplings or mature trees).  Therefore we
should be promoting landuse=forestry (unambiguous) and landcover=trees
(somewhat ambiguous, but
for use where forestry isn't applicable), or whatever we eventually (3o
years from now?) decide upon.  To
a large extent, the problem we currently have with landuse=forest is that
it should have originally been
named landuse=forestry to prevent the ambiguous usage we now have with

It's no good arguing that the wiki should explain ambiguous tags because
people with English as a first
language often do not look at the wiki (they assume the tag means what it
says).  It would help,
though, if editor presets offered extra guidance (at least at the first
use) such as pointing out that
landuse=forestry and landcover=trees are possible alternatives and which
should be used in which
circumstance (again, assuming those are the two we decide upon 97 years
from now).

It's no good saying that a mass edit can fix it.  A mass edit (along with
changes to editor presets and
renderers) could only work if the tag were unambiguous and used correctly
in 99.99% of cases.  Unless
the proposer is willing to personally survey each use and decide whether or
not the new tag is
applicable, mass edits of ambiguous tags won't work.  A mass edit might be
sensible with a tag that is
mis-spelled, but it is not sensible for a tag which has been used to map
two or more different types of object
that we now realize should be mapped differently.

I now give you a quote from Fred Brooks Jr:

The management question, therefore, is not *whether* to build a pilot
system and throw it away. You *will*
do that. […] Hence

*plan to throw one away; you will, anyhow.*
He was writing of software projects.  And he's since partially recanted by
saying it's applicable only to
waterfall development.  But the concept still applies here.  The first time
you tackle a software project
(or design a mapping system like OSM) you don't fully comprehend the
requirements or how it will
actually be used.  What you end up with is imperfect, but you also learn
how to do it better the next time.

OSM evolved in an ad-hoc way.  The result is a set of tags which aren't
orthogonal and which aren't
all intuitive.  The ONLY way you can fix it is with a new project that
starts from scratch and requires
everything to be mapped from scratch (otherwise all you've done is fixed
"spelling errors" in tag names).
And, if you do that, even if what you come up with is perfect it will not
remain so because people keep
finding new types of things to match.  There isn't going to be a "next
time" with OSM (feel free to
prove me wrong by forking it and encouraging people to enter all the data
from scratch).

The best we can do with things like landuse=forest is come up with two or
more new tags, promote
the new tags, maybe have editors warn that the old tag is deprecated, and
let the old tag fade away.

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