# [OSM-talk] talk Digest, Vol 48, Issue 77

David Ebling dave_ebling at yahoo.co.uk
Thu Aug 28 13:46:58 BST 2008

```Peter,

The same idea has occurred to me also. I think far from developing this being a waste of time, I think it is highly desirable from the point of view of avoiding multiple ways sharing a set of nodes, which makes editing a nightmare. It seems all round the most elegant solution for multiple areas to me, and I agree, it should include the multipolygon functionality.

Regards,

Dave

---original message follows---
Personally I prefer to recommend that you definer the area of grass using a
separate way that uses the same nodes as the residential road, but which is
certainly a separate way from the road. You may prefer to define it as a
separate way using separate nodes as this can make editing easier in the
short term, however Richard explained yesterday on talk how to use '/'
to
select from the different ways associated with the same node which I will
investigate. Using the approach you have tried is definitely to be
discouraged imho, and mixes up two different things into one way.

As a longer term discussion I am interested in morphing the
'multi-polygon'
relation into a 'polygon' relation so it can be used as an alternative
ways
of defining areas. The relation would need to allow a number of linear
features to form the boundary of the area. The relation would then hold the
tags that are associated with the area (in this case 'landuse=grass').
The
relation could also be able to refer to zero or more 'inner' areas
which can
be defined in a similar way to define 'holes' in polygons.

This approach allows a single 'edge' to be part of a number of areas (I
gave
the example of the edge of a park also being the boundary for the borough in
a previous post). Currently the approach of using boundary:left=Ipswich for
part of the boundary is not compatible with have a single way defining the
area of the park. I am also advocating that we dump the current boundary
left: and right: tagging in favour of using the 'boundary' relation for
boundaries.

I might come up with a technical demonstrator for this in the near future so
explore how it might work in practice. There is more discussion on polygons
and relations here:
http://wiki.openstreetmap.org/index.php/Talk:Relation:multipolygon

And the boundary relation here:
http://wiki.openstreetmap.org/index.php/Relations/Proposed/Boundaries

If this approach was used we would be able to run with both coding systems
in the short term and possibly then deprecate ways being used for areas and
boundaries in the longer term.

Any other thoughts? Am I wasting my time on this idea, or do others see
value in it? Is so would it be useful to produce some trial rendering or
would someone like to make osmarender or Mapnik handle it?

Regards,

Peter(Ito)

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