[OSM-talk] Abandon all ways: a polemic

Laurence Penney lorp at lorp.org
Mon Mar 19 23:09:51 GMT 2007

Martijn van Oosterhout wrote:
>> 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.

Good abstractions that deserve a place in a UI need not be part of the 
data model.

My ideal editor would give much more prominence to topology, so make 
egdes (in the graph theory sense) and nodes the main selectable things 
in a JOSM-style UI. A curved section of road between two nodes would 
be selectable as easily as a straight segment between them; and one 
would be able to apply tags to the curved road as easily as the 
straight one.

> 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 performance and storage load on the db would be roughly the same, 
I think. With a compressed string stored as an int, you'd be selecting 
for segments having a particular ID number, as happens now.

>> 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.

A senior source told me that OSM can have multiple tags with the same 
key, and it's JOSM that can't handle them! The example I mentioned has 
Gloucester Row on the street signs, and is how letters are addressed; 
Suspension Bridge Road is nowhere to be seen on the street, but is 
what you see on the A-Z map (sorry, I looked!) and some locals do know 
that name too. I don't think loc_name works well here: they are both 
good, official names for the street.

> 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.

An editor could highlight all other segments which share (selectable) 
characteristics of a chosen segment. So by selecting the "Gloucester 
Row" segment I could click on different tags in the info panel to 
highlight the whole of Suspension Bridge Road or the B3129.

> What about areas btw?

How is representing areas with segments any better or worse than with 
ways? A set of directed segments can enclose an area perfectly well, 
including multi-polygons with holes.


-- Laurence

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