[Talk-GB] UK Rights of Way - WikiProject

[Andrew M. Bishop]

Andy Street <mail at andystreet.me.uk> writes:

> On Fri, 2012-05-04 at 14:32 +0100, Andrew Chadwick wrote:
> I'd agree that generic consumers will struggle with highway=path,
> designation=* but that is a wider OSM issue and not limited to the
> path/footway, etc. debate. Anyone using OSM data should be
> pre-processing it to take into account local laws/customs and their
> particular use case. For example, you are probably going to come a
> cropper if you go around assuming that roads across the globe without an
> explicit maxspeed tag all have the same default value.

As the author of a consumer of OSM data I for one would prefer it if
there was a single set of tags worldwide.  In my case the consumer of
the data is Routino a router for OSM data (http://www.routino.org/).

My personal opinion is that the biggest risk to OSM's future is if we
don't agree on a subset of tagging rules to be used worldwide.  The
idea that there could be a pre-processor to handle local laws and
customs is impractical.  There are literally hundreds of regions that
might use their own tagging rules each of which needs to be defined by
a geographical region and list of rules.  Each consumer of data then
needs to implement the full set of pre-processor rules.

With a single set of rules a way can be taken from an OSM XML file and
it will be immediately apparent who is permitted to use it.  With a
pre-processor it is necessary to take the way from the file, search
through the whole file to find the nodes that are referenced by it,
search through all defined regions to determine which one the nodes
belong to and then apply the selected pre-processor.

One thing that we shouldn't lose sight of is that each item in OSM is
created once and edited a few times by a small number of editors but
used many hundreds of time each day by many dozens of data consumers.
Since the number of times the data is read far exceeds the number of
times the data is written (by orders of magnitude) the complexity
should be in the writing side and not the reading side.


> I also fail to see how highway=footway/cycleway/bridleway would help
> here either. Looking at this[1] wiki page shows all manner of different
> default permissions dependent on different geographical regions. The
> only way I can see to completely eradicate this problem would be a full
> set of access tags (foot=*, horse=*, etc) on every way but that is not
> something either of us would find desirable.

A set of worldwide default permissions would be an alternative to
having every way tagged with every possible traffic type.  This would
then need just a single pre-processor step that can be applied without
geographical constraints.

-- 
Andrew.
----------------------------------------------------------------------
Andrew M. Bishop                             amb at gedanken.demon.co.uk
                                              http://www.routino.org/