[OSM-dev] License change simulation

[Frederik Ramm]

Hi,

    I'm sure I have announced this somewhere a while ago but cannot find 
it now, so pardon me if you're reading this for the second time.

A student from Karlsruhe, Jakob Altenstein, has done his Bachelor thesis 
on the OSM license change, looking at ways to compute the effect of the 
license change (deleting data that cannot be relicensed), and 
visualizing them. I was the co-supervisor for the thesis.

Apart from his thesis, which you can read here (if you read German):

http://checkout.yourweb.de/thesis/Jakob_Altenstein_Thesis.pdf

Jakob has also produced a software called "ODBL simulator" which is open 
source and available here:

svn.openstreetmap.org/applications/utils/filter/odblsimulator

The software takes a full history extract (see Peter's posting 
http://lists.openstreetmap.org/pipermail/dev/2011-May/022624.html for 
how to get/make them), and can then generate two different kinds of 
output: A what-if .osm file that only contains data that can be 
relicensed, or a full current .osm file that has extra tags on all 
objects indicating what their relicensing situation is. That .osm file 
can then be processed with any of our standard renderers (Jakob has used 
Maperitive) to produce a map where "endangered" objects are highlighted.

The code isn't perfect (hard-coded file names and stuff) but works all 
right. It even has a method for salvaging information from later 
versions when an intermediate version of something cannot be relicensed.

It is still very much unclear what algorithms, if any, will be used when 
we really switch our license. But the ODBL simulator is a great tool to 
visualize the consequences of choosing one or another method, and I hope 
that others will jump in and add more algorithms that handle data loss 
in different ways.

Feel free to amend the software in SVN; while I assume that Jakob will 
still watch things with interest, he's busy with non-OSM stuff now and 
unlikely to continue work on this.

Bye
Frederik