[OSM-newbies] Definition of ways, dupes, etc.

[Sascha Silbe]

Hi!

I'm currently writing a simple (offline) map viewer with support for OSM 
data in an SQL database.
While trying to add OSM support, I encountered a few issues. If my 
questions have been answered before, please just direct me to the exact 
location of the answer. Since I'm curently behind a 33k6 modem, browsing 
the archives is no fun at all. I've read most of the Wiki (regarding the 
questions asked here, at least), though.

1. There are loads of dupes for each element type (i.e. nodes, segments, 
segment references; haven't checked ways for equality yet). Is this 
intended? What's the reason?
2. What about the negative IDs? Do they indicate something special?

I'm also puzzled about the relationship between real-life ways and the 
OSM element type "way". To get an idea of it, I'll ask some questions:

1. How are a full motorway (with differing number of lanes) and its 
links represented in OSM (esp. if it has bridges over other ways)?
2. How is a circular way (e.g. "Berliner Ring" in Tübingen) represented 
in OSM?
3. How are tags set that apply to the full way (e.g. highway=motorway)?
4. How are tags set that apply only to parts of the way (e.g. lanes=2)?
5. How is an area (e.g. a park) represented in OSM?
6. How do I determine all the segments (and only those) of a given 
motorway?
7. How do I determine the area and tags belonging to a given park?
8. When rendering, how do I determine if a way represents a "real" way 
(see circular way example above) or an area?
9. What do segments that are not part of ways represent?
10. What do ways without a highway tag represent?

BTW, why is the "highway" tag called that instead of something more 
generic (like "class" or "type")? "highway=track" looks funny. :)

CU Sascha

-- 
http://sascha.silbe.org/

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