[Tagging] Bad tag: demolished=<date>: move to a) modify, b) strongly discourage

Andrew Chadwick (lists) a.t.chadwick+lists at gmail.com
Thu Jun 27 17:23:02 UTC 2013

I've just been reminded of the existence of


which nobody is using very much, and which nobody seems to be
maintaining. I hope nobody will start using it, for it seems to me
that this tag will generate bad data:

  i. If an object is demolished, its other tags should be removed, or
at least or "namespaced out" in a matter similar to what we should now
be doing for disused=yes and abandoned=yes. Not doing so will confuse
map data consumers, creating situations where demolished objects are
used for routing or rendering;

  ii. The date format is Wrong: see http://xkcd.com/1179/ (we should
be using partial ISO dates too, in case the day or the month of
demolition is not known);

  iii. We should not in general be mapping features which are no
longer physically relevant. Demolished items by their very nature are
not relevant, and are potentially not verifiable. OSM a map of the the
world as it is in reality, verifiably and currently, and not a
historic map. If a demolished item is currently a brownfield site, it
should be tagged as a new object with those details. If it's now a
construction site, tag it as that.

Therefore I propose:

a) Modification of this page to avoid bad data creeping into the database, by:

  1. Rewriting it as a namespace in a similar manner to abandoned and
disused, addressing [i];
  2. Altering the date specification to be Right, namely the ISO 8601
date formats, addressing [ii].

b) Strongly discouraging its use altogether, addressing [iii].

Andrew Chadwick

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