[OSM-dev] License change simulation
frederik at remote.org
Thu May 19 13:15:19 BST 2011
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):
Jakob has also produced a software called "ODBL simulator" which is open
source and available here:
The software takes a full history extract (see Peter's posting
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.
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