[OSM-talk] access=destination valid only in one direction

[Claudius]

Am 11.07.2009 08:23, Marcus Wolschon:
> On Fri, Jul 10, 2009 at 5:03 PM, Tobias Knerr<osm at tobias-knerr.de>  wrote:
>> Stanislav Brabec wrote:
>>> Is there a way how to map a street with access=destination valid just
>>> only for one direction? In the reverse direction it is a standard drive
>>> through street.
>> Using my proposal
>> http://wiki.openstreetmap.org/wiki/Proposed_features/Extended_conditions_for_access_tags
>> it would be
>>
>> access[forward] = destination
>>
>> (or access:forward = destination, depending on what syntax people like
>> better)
>>
>> Of course that's way direction dependent.
>
> and it does not work NOW.
> Once it MAY be accepted in this OR a modified form (sometime in the future),
> then used in a significant number of places (much, much later),
> then the first programs may get a feature-request to implement support for it
> (where the normal access=destinationis already a bit tricky and not all
> programs have internal datastructures that allow such a construct at all) and
> quite a while later some developer may find the time to actually implement
> and test it. Then people will start filing bugs as it does not work
> perfectly the first time and later these bugs may be fixed.
> THEN it will be supported in SOME programs while others will still ignore it
> completely.
>
> Whereas drawing 2 ways works now. These 2 ways may even share
> exactly the same nodes and if they share the same nodes even turning
> around at any of these nodes will work.

I think forcing *everything* to be backward compatible does hinder 
evolution sometimes.
You could also start tagging access:forward and eventually routers *have 
to* support it because it's used in such big numbers.

And, besides, drawing two ways simply does not reflect reality on the 
ground and as such is a wrong information that cannot be healed later 
on. It's easier for a router-preprocessor to turn access:forward into 
two ways internally.

Claudius