[OSM-talk] Abandon all ways: a polemic

Martijn van Oosterhout kleptog at gmail.com
Mon Mar 19 22:15:34 GMT 2007


On 3/19/07, Laurence Penney <lorp at lorp.org> wrote:
> One geeky horror of the idea may be that lots of segments with,
> broadly, the same set of tags is a bad idea in terms of data
> redundancy. The two obvious problems are a bloat in data storage needs
> (we'd store for some ways 100s of times the data in key-value
> strings), and an increased risk of lack of consistency (one segment
> marked Main St instead of Main Street).
>
> But can't this be sorted out by, at the back end, having good data
> compression, storing identical strings just once; and at the front
> end, giving editing apps easy ways to copy & paste a set of tags from
> one segment to others, and to encourage easy re-selection of strings
> from the locality?

It seems to me you're just doing ways the hard way. Ways are a good,
easy to understand abstraction. You apply the same tags to many
segments. If I have a way with 20 tags and I insert a node into it,
it's easier to think of it as a way that got an extra segment, than as
a new segment that got 20 tags added to it.

> Keeping ways might be justified if it helped the noble causes of
> route-finding and map rendering. But on balance, ways don't help:

I think ways do help on the storage requirement front. It's nice to
know while searching along a freeway that the next 200 segments are
all the same without have to check the tags on each one.

> The common problem of giving a road multiple names needs fixing. Our
> main editor, JOSM, hasn't cracked it. I simply don't think I'll get
> around to tagging correctly the single stretch of road near me that is
> Gloucester Row, Suspension Bridge Road and the B3129.

How do you want it to work? The B-tag is obviously a ref, and you can
specify both a name and a local name. You can add as many tags as you
like, you just can't add two with the same key. That's nothing to do
with JOSM, that's the backend.

> Bus routes were also mentioned in the same thread. I don't like the
> idea of adding ways for these. What's up with adding a "bus_route=37"
> tag to each of the segments the bus runs through? (Ok, some
> directional or segment ordering stuff might have to be added, but
> segment tags are the perfect place to add that too.)

I think it's a good idea actually, but we shouldn't get rid of ways.

I think ways help data consistancy way more than they hurt it. I can
save the map I'm working on and verify that most streets appear
exactly once, as they should. If the names were stored directly on the
segments, there'd be no easy way to verify that all the segments with
that name actually join up.

What about areas btw?

Have a nice day,
-- 
Martijn van Oosterhout <kleptog at gmail.com> http://svana.org/kleptog/




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