[Tagging] Extended tagging schema - my thoughts

[Tobias Knerr]

On 10.08.2012 16:47, Rob Nickerson wrote:
> I've been thinking a bit more about this and would like to improve on my
> initial thoughts from yesterday. So expanding on the existing
> opening_hours type tag, I would like to suggest the following format for
> extended access tags:
> 
>   * <rule>:<vehicle>=<condition1> <value1>; <condition2> <value2>...

Have you seen the "Conditional restrictions" proposal that was linked
here yesterday?

http://wiki.osm.org/Proposed_features/Conditional_restrictions

It is basically the same idea. The most important difference is that it
uses a ":conditional" suffix. This makes it backwards compatible, unlike
your solution which would put things like "120; wet 80" into the
established maxspeed tag.

>  * maxspeed=120
>  * maxspeed:hgv=80

These would look the same with "Conditional restrictions".

>  * maxspeed=120; wet 80

This would become
maxspeed = 120
maxspeed:conditional = 80:wet

>  * bicycle=yes; 10:00-18:00 no

This would be
bicycle = yes
bicycle:conditional = no:(10:00-18:00)

I think it would be a better idea to provide feedback to the author of
that proposal to address any remaining issues. It is (imo) much more
likely to be accepted by the community for the simple reason that it
doesn't break existing functionality.

(I don't think that you may _never_ do incompatible changes, but if
there are two essentially equivalent approaches, then the one that is
backwards compatible would of course be preferable.)

> Possible issues:
> 1. How to include 'forward', backward'

The proposal linked above uses <rule>:<vehicle>:<direction>, which has
the advantage that editors' existing support for reversing ways with
direction-dependent restrictions.

Tobias