[Talk-us] understanding administrative boundary relations

[Ray Kiddy]

On Fri, 4 Sep 2015 14:11:26 -0500
Toby Murray <toby.murray at gmail.com> wrote:

> On Fri, Sep 4, 2015 at 1:37 PM, Ray Kiddy <ray at ganymede.org> wrote:
> >
> > Strangely, I am finding that some of the cities in California _are_
> > in the system, but as ways and not as relations. This seems odd,
> > but we will see.
> 
> Well the primary reason to use relations in boundaries is to reduce
> duplication. So if two cities share a border, the same way can be used
> in both relations. Sometimes people even use roads or streams or other
> physical ways as part of boundary relations. I personally usually
> avoid this because I like having boundary relations completely
> separate from other things so that they are easier to update in the
> future. So for a city that is not part of a metro area with adjoining
> cities, it is perfectly fine to just used a closed way instead of a
> relation for the boundary. At the end of the day, both ways and
> relations generally get turned into either linestrings (if linear) or
> multipolygons (if closed) in things like a postgis database or a
> shapefile.
> 
> Toby
> 

So, there is nothing that a relation brings to the table that a way
does not? I mean, it is clear that for the purposes of drawing, they
are the same. But then are they really just the same?

I am tempted to try to add relations for these that refer to the ways,
moving the associated data appropriately, but then I like to do things
like re-normalizing databases and it is sometimes not such a good
idea....

So, I will believe you if you say that ways are just aliases for
relations. Is this the case?

- ray