[Tagging] Twisted semantics of entrance=exit and entrance=emergency

[Martin Fischer]

On 6/10/22 6:59 PM, Tobias Knerr wrote:
> From a data modelling perspective, it is nicer for each element to 
> have exactly one main tag.

Generally speaking I agree but when it comes to entrances and exits, 
shoehorning both into the same main tag doesn't improve anything.

Introducing the exit key as per my proposal actually improves the 
expressiveness of the tagging scheme because you can combine exit=no 
with any entrance=*, e.g. consider the semantic differences between:

* an entrance with entrance=main + exit=no
* another entrance with entrance=yes + exit=no

A routing software can take advantage of that (e.g. when routing to the 
building it could prefer entrance=main over entrance=yes) when leaving a 
building it could detect that both entrances may not be used as exits.

As opposed to having to come up with monstrosities like 
entrance=main_no_exit or entrance=yes_no_exit.

Best,
Martin