[OSM-talk] Suggestion: fallback tag

[Steve Bennett]

Hi all,
  As we all know, you don't "tag for the renderer". However, you want your
map data to render nicely now, and you want correct map data in the long
term.

Suggestion: introduce a "fallback" tag.

For example, around my city there are little "reserves" - patches of grass
reserved by the government for future development such as freeways or train
lines. They often get tagged "leisure=park", but say I want to start tagging
them "landuse=reserve" instead. Suddenly, instead of being green on mapnik,
it will be white again - unrecognised tag.

Solution: tag it like this:
landuse=reserve
fallback:leisure=park

That's pretty simple logic to explain to any renderer or editor, and it
gives people a way to avoid the temptation of "tagging for the renderer",
and allows them to tag for the future instead.

What do people think? (No comments on how to tag land reserves, it's just an
example...)

(This case is slightly complicated by the fact that the two tags - landuse
and leisure - are different. Perhaps a more explicit
fallback:landuse=leisure:park would be clearer.)

Steve
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